Preheat your oven to 375°F and line a 9x13-inch baking dish with parchment paper. This simple step ensures the bars lift out easily after baking.
Combine the flour, white and brown sugars, and salt in a mixing bowl.
Add the softened, cubed butter to the dry ingredients. Use a fork to mix until crumbly, then press together with your hands until the dough starts to clump.
Spread this mixture evenly in the prepared baking dish, pressing it into a smooth, even layer for the crust. Bake for 20 minutes, then let it cool for about 10 minutes while you work on the orange filling.
In a large mixing bowl, whisk together the eggs and fresh orange juice until fully blended. Add the orange extract, zest, flour, and baking powder, whisking until smooth.
Gradually incorporate the sugar, whisking until the mixture is well combined.
Pour the orange filling over the slightly cooled crust and bake for another 60 minutes. The filling should be set but still slightly jiggly in the center. Let it cool at room temperature for 15 minutes, then refrigerate while you prepare the dreamsicle topping.
Heat the orange juice in a small saucepan until steaming, then remove from heat and stir in the gelatin. Allow it to sit for a few minutes to thicken, then briefly reheat to dissolve the gelatin fully. Set aside to cool slightly.
In a mixing bowl, beat the cream cheese until smooth. Add the sweetened condensed milk and sour cream, blending until creamy.
Fold in the vanilla extract and orange zest. Slowly incorporate the gelatin mixture, stirring until fully combined and smooth.
Remove the orange bars from the fridge and pour the dreamsicle mixture evenly over the top. Use a spatula to spread it smoothly.
Garnish with extra orange zest and cover the dish with plastic wrap. Chill in the refrigerator for at least 6 hours or overnight to allow the layers to set completely.
Once chilled, lift the bars out of the baking dish using the parchment paper. Slice into 12 even pieces and serve. Watch as everyone takes a bite and smiles with delight!