Step 1: Preheat and Prepare : Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with paper cupcake liners. Set out all ingredients to reach room temperature for even mixing.

Step 2: Mix Dry Ingredients : In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

Step 3: Cream Butter and Sugar : In a large mixing bowl, use a hand or stand mixer to beat butter and sugar together until light and fluffy (about 2–3 minutes). Scrape down the sides of the bowl occasionally.

Step 4: Add Eggs and Vanilla : Beat in the eggs, one at a time, mixing well after each addition. Add vanilla bean seeds (or paste) and mix until fully incorporated.

Step 5: Combine Wet and Dry Ingredients : Add the dry ingredients to the butter mixture in three additions, alternating with milk and sour cream. Begin and end with dry ingredients. Mix just until combined — do not overmix.

Step 6: Fill and Bake : Divide the batter evenly among the cupcake liners (about 2/3 full). Bake for 18–20 minutes, or until a toothpick inserted in the center comes out clean. Cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.

Step 7: Make the Strawberry Buttercream : Puree fresh strawberries in a blender, then strain to remove seeds. Beat softened butter on medium speed until creamy (about 1 minute). Gradually add powdered sugar, 1 cup at a time, beating on low. Add strawberry puree, vanilla extract, and salt. Beat on medium-high for 2–3 minutes until fluffy and smooth. If too thin, add more sugar; if too thick, add a teaspoon of milk.

Step 8: Frost the Cupcakes : Once cupcakes are completely cooled, pipe or spread the strawberry buttercream on top. Garnish with a small fresh strawberry slice, or a sprinkle of edible glitter for a festive touch.