Mix strawberries, sugar, lemon juice, cornstarch, and vanilla extract together and let the mixture sit for 10 minutes so the filling thickens slightly before baking.
Whisk flour, baking powder, and salt together in one bowl. In another bowl, beat butter and brown sugar until fluffy, then mix in eggs and extracts before combining with dry ingredients to form a soft dough.
Press two-thirds of the dough into a parchment-lined baking pan and spread the strawberry filling evenly across the surface for balanced flavor in every bite.
Crumble the remaining dough over the strawberry layer and sprinkle coarse sugar on top to create a lightly crisp finish after baking.
Bake at 350°F (175°C) for 35 to 38 minutes until the top turns lightly golden and the strawberry filling bubbles around the edges.
Cool completely before slicing so the filling sets properly and the bars hold their shape cleanly during serving.