Toss sliced strawberries with 1/2 cup sugar and lemon juice; let them sit 20–30 minutes to release juices.
Heat oven to 425°F. Line a baking sheet with parchment.
Whisk flour, 3 tbsp sugar, baking powder, and salt in a large bowl.
Cut in the cold butter until the mixture looks like coarse crumbs with pea-sized bits.
Pour in 3/4 cup heavy cream and stir just until a shaggy dough forms; do not overmix.
Turn dough onto a lightly floured surface. Pat to about 3/4 inch thick and cut into 8 rounds or squares.
Arrange on the baking sheet. Brush tops with a little cream and sprinkle with 1 tbsp sugar.
Bake 12–15 minutes, until golden. Cool on a rack for 10 minutes.
Whip 1 cup cold cream with powdered sugar and vanilla to soft peaks.
Split shortcakes. Spoon on berries with their syrup, add whipped cream, cap, and serve right away.