Preheat oven to 375ºF (190ºC). Line an 8X8 baking pan with aluminum foil and spray with nonstick cooking spray.
Add flour (1 1/2 cups), brown sugar (1/2 cup), baking soda (1/2 teaspoon), baking powder (1/2 teaspoon), and salt (1/4 teaspoon) to a medium and whisk until ingredients are evenly combined. Add the butter (1/2 cup) and combine until the mixture is the size of peas and is crumbly. Reserve 3/4 cup of crumb mixture and set aside to use for the topping. Press the remaining crumb mixture into the prepared baking pan. Set aside and prepare to fill.
Add the sour cream (1/2 cup), sugar (1/4 cup), 1 tablespoon of flour, egg (1), and vanilla (1/2 teaspoon) in a large bowl and mix until all the ingredients are evenly combined. Spread the filling over the prepared crust. Drop spoonfuls of strawberry pie filling evenly over sour cream filling. Gently swirl pie filling with a sour cream mixture with a spoon. Sprinkle reserved crumb mixture evenly over top.
Bake in the preheated oven for 25-28 minutes or until the top of the bars begin to brown and the center of the bars is "set". Cool completely and serve. Store any leftovers in the fridge.