Preheat your oven to 350°F and line two 12-cup muffin pans with cupcake liners. Ensure your eggs are at room temperature and measure out all dry ingredients. Sift flour with the baking powder to ensure even distribution.

In a large mixing bowl, beat the softened butter and sugar together for 2-3 minutes until light, fluffy, and pale yellow. Scrape down the bowl occasionally.

Add the room-temperature eggs one at a time, beating well after each addition. Mix in the vanilla extract. Alternate adding the dry ingredients and milk, starting and ending with dry ingredients. Mix until just combined.

Divide the batter evenly among the cupcake liners, filling each about two-thirds full. Bake for 20-25 minutes until a toothpick comes out clean. Cool in the pans for 5 minutes, then transfer to a wire rack.

While cooling, dice strawberries and toss with sugar and lemon juice. Let sit for 15 minutes to release juices.

In a clean bowl, beat softened butter for the buttercream for 2-3 minutes. Gradually add powdered sugar, then heavy cream, vanilla, and salt. Beat until fluffy and holds stiff peaks.

Spread a thin layer of buttercream on each cooled cupcake. Pipe a border of frosting around the edge, leaving the center open. Spoon strawberries into the center of each cupcake.