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Light fluffy lemony cupcakes with a little crunch from poppy seeds topped with a beautiful fresh blackberry buttercream frosting.
These moist and flavorful cupcakes offer a perfect balance of sweetness and tartness, making them a refreshing and indulgent choice for any dessert lover.

Easy Cupcakes from a Box Mix
These cupcakes are super simple to make because they are from a box mix. All you need are a few extra ingredients and you’ll get perfectly flavored and fluffy cupcakes every time.
Using a box mix \provides a convenient and time-saving option without compromising on flavor. It ensures a quick and foolproof baking experience, allowing you to enjoy the delightful combination of citrusy brightness and poppy seed crunch without the hassle of measuring and mixing ingredients from scratch.
Cupcake Ingredients
- Lemon Cake Mix
- Eggs
- Canola oil
- Fresh lemon juice and lemon zest
- Water
- Poppy seeds
Blackberry Buttercream Ingredients
- Fresh blackberries
- Butter
- Confectioners’ sugar (also called powdered sugar)
- Cream of tartar
Let’s Make Lemon Poppy Seed Cupcakes with Blackberry Buttercream
Cupcakes
- Preheat the oven to 350°.
- Place cake ingredients into a mixing bowl and mix on low speed for 30 seconds.
- Increase mixer speed to medium-high and mix for 2 minutes.
- Pour the mixture into a lined muffin/cupcake tin.
- Bake for 22 minutes or until a toothpick comes out clean.
- Cool cupcakes at room temperature before frosting.
Blackberry Buttercream
- Place blackberries into a small skillet with 1 tbsp water and 1 tbsp honey.
- Heat on medium until berries break down. Watch them so they do not burn.
- Remove the berries from the heat.
- Using a fine mesh strainer, press the berries so the berry juices run into a small bowl.
- Discard the berry pieces in the strainer and set berry juice aside or in the refrigerator to cool.
- Add the butter to a mixing bowl and mix until smooth.
- Mix in cream of tartar and ½ cup confectioners’ sugar.
- Continue to mix in sugar ½ cup at a time.
- Add 2-3 tbsp of blackberry juice to the buttercream.
- Transfer the buttercream to a pastry bag with a frosting tip.
Questions
To make the cupcakes taste homemade, rather than from a box mix, always add 1 additional egg than the box mix calls for. This works with any type of boxed cake mix.
This happens for mainly 1 or 2 reasons. First, because you filled the muffin tin with too much batter. Fill each 1/2 to 3/4 of the way. Avoid overfilling them. The second reason is that the cupcakes were overmixed causing too much air during baking. Mixing time is important in making any baked items.
Freeze it! Buttercream freezes beautifully. It will last up to 3 months wrapped in plastic wrap. To thaw, let it sit overnight in the refrigerator.
Krazy Kitchen Mom Tips
- Depending upon the size of the lemons, it will take 2-3 large lemons to yield 1/3 cup.
- Be sure that the blackberry juice is completely cooled before adding it to the buttercream.
- Store frosted cupcakes in an airtight container in the refrigerator.
- You can also freeze unfrosted cupcakes wrapped in plastic wrap for 3-4 months. To thaw, let them sit in the refrigerator overnight or on the kitchen counter. Let them thaw completely before frosting them.
More KKM Sweet Recipes
- Peaches and Cream
- Skillet Blongie Cookie
- Pan-Banging Chocolate Chip Cookies
- No-Bake Chocolate Hazelnut Mousse
Lemon Poppy Seed Cupcakes with Blackberry Buttercream
Ingredients
LEMON POPPY SEED CUPCAKES
- 1 lemon cake mix
- 4 eggs
- 1/3 cup fresh lemon juice
- 1/3 cup canola oil
- 2/3 cup water
- 1 tbsp lemon zest
- 2 tbsp poppy seeds
BLACKBERRY BUTTERCREAM
- 1/2 pint fresh blackberries
- 1 cup butter – softened at room temperature
- 3 cups confectioners' sugar
- 1 teaspoon cream of tartar
Instructions
LEMON POPPY SEED CUPCAKES
- Preheat the oven to 350°.
- Place cake ingredients into a mixing bowl and mix on low speed for 30 seconds.
- Increase mixer speed to medium-high and mix for 2 minutes.
- Pour the mixture into a lined muffin/cupcake tin.
- Bake for 22 minutes or until a toothpick comes out clean.
- Cool cupcakes at room temperature before frosting.
LEMON POPPY SEED BUTTERCREAM
- Place blackberries into a small skillet with 1 tbsp water and 1 tbsp honey.
- Heat on medium until berries break down. Watch them so they do not burn.
- Remove the berries from the heat.
- Using a fine mesh strainer, press the berries so the berry juices run into a small bowl.
- Discard the berry pieces in the strainer and set berry juice aside or in the refrigerator to cool.
- Add the butter to a mixing bowl and mix until smooth.
- Mix in cream of tartar and ½ but confectioners’ sugar.
- Continue to mix in sugar ½ cup at a time.
- Add 2-3 tbsp of blackberry juice to the buttercream.
- Transfer the buttercream to a pastry bag with a frosting tip.
Notes
- Depending upon the size of the lemons, it will take 2-3 large lemons to yield 1/3 cup.
- Be sure that the blackberry juice is completely cooled before adding it to the buttercream.
- Store frosted cupcakes in an airtight container in the refrigerator.
- You can also freeze unfrosted cupcakes wrapped in plastic wrap for 3-4 months. To thaw, let them sit in the refrigerator overnight or on the kitchen counter. Let them thaw completely before frosting them.
- In order to make the cupcakes taste homemade, rather than from a box mix, always add 1 additional egg than the box mix calls for. This works with any type of boxed cake mix.
- This happens for mainly 1 or 2 reasons. First, because you filled the muffin tin with too much batter. Fill each 1/2 to 3/4 of the way. Avoid overfilling them. The second reason is that the cupcakes were overmixed causing too much air during baking. Mixing time is important in making any baked items.
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