In a medium saucepan over medium heat, cook strawberries, sugar, vanilla, and lemon juice, stirring occasionally, until strawberries begin to break down and sugar dissolves, 3 to 4 minutes. Continue to simmer, stirring occasionally, until mixture is slightly thickened and resembles strawberry jam, 12 to 15 minutes. Stir in lemon zest and a pinch of salt. Remove from heat.

Transfer to a standard blender (or use an immersion blender) and puree until smooth. Let cool.

Arrange a rack in lower third of oven; preheat to 325°. Line a 9" square baking pan with parchment.

In a medium heatproof bowl, microwave butter and chocolate melts in 30-second increments, stirring between each, until melted and smooth, about 90 seconds total.

In the large bowl of a stand mixer fitted with the whisk attachment, beat egg, egg yolk, sugar, and freeze-dried strawberries (if using) on medium-high speed until pale and fluffy. Beat in vanilla and 1 cup (140 g.) strawberry puree; reserve remaining puree. Gradually beat in melted chocolate until smooth.

Switch to the paddle attachment. Sift in flour, salt, and baking powder and beat on medium-low speed until just combined. Add food coloring, a few drops at a time, and beat until desired color is reached, being careful not to overmix. Pour batter into prepared pan.

Bake brownies until lightly browned around the edges and a tester inserted into the center comes out clean, 35 to 40 minutes. Let cool.

In a medium heatproof bowl, microwave chocolate melts and cream in 30-second increments, stirring between each, until melted and smooth, about 2 minutes total.

Stir in ¼ cup strawberry puree. Let cool.

Spread ganache on top of cooled brownies. Top with strawberry slices and crushed freeze-dried strawberries (if using).