Preheat oven to 375F/ 190C. Butter or spray with a non-stick baking spray an 8 or 9-inch square baking pan, then line with parchment paper so it comes up the sides slightly. (This will make it easier to remove the whole pan of bars for easier cutting.)
In a medium bowl, gently combine all the ingredients for the strawberry filling and set aside.
In the bowl of a food processor fitted with the blade attachment, add the flour, sugar, lemon zest, salt and cold butter and pulse until it resembles coarse crumbs. Then add the egg, vinegar, and vanilla and pulse a few more times until it just starts to come together. It should still be somewhat shaggy. If it's too dry add another teaspoon of vinegar.
Then spread the 3/4 cup of lemon curd evenly over the crust and spoon the strawberry mixture on top of the curd.
Place the pan in the refrigerator and chill about 15-20 minutes. (The freezer can be used to speed the process up.) Then place in the center of the preheated oven and bake about 55 minutes until the filling is bubbly and the crust is golden brown on top.
*If making the lemon curd yourself, here's a great recipe- https://atreatlife.com/2019/03/30/lemon-curd/
*I cut the strawberries into thin slices to be able to see the pretty shape better, but you can quarter them too.
*chilling the bars before and after baking helps to keep the dough from spreading too much on top and makes it easier to cut them afterwards.