Place flour, sugar, butter and salt in a food processor. Pulse 5-6 times until mixture is crumbly.
1 ½ cup flour, ⅓ cup sugar, ½ cup butter, ¼ teaspoon salt
Place mixture in a greased 9 x 13 baking dish. Press flour firmly down with hands or the bottom of a flat measuring cup. The mixture will be very dry.
Place in preheated oven for 12 minutes.
Filling
Combine sweet and condensed milk, egg yolks, lemon zest and lemon juice.
1 can sweet and condensed milk, 2 egg yolks, ½ cup lemon juice, 1 tablespoon lemon zest
When crust comes out of the oven, pour blueberries directly over hot crust.
3 cups blueberries
Spoon filling mixture over blueberries. It's okay it it doesn't cover every area.
Topping
In another bowl, combine flour, sugar, melted butter and lemon zest. Mix with a spoon, just until the butter is mixed in and then continue mixing with your fingers. You want a crumbly mixture.
¾ cup flour, ½ cup sugar, ⅓ cup butter, 1 teaspoon lemon zest
Sprinkle crumbles over the top of lemon filling
Bake in 350 degree oven for 40 - 45 minutes. The topping should be browned and the mixture bubbly.
Allow bars to fully cool at room temperature. Then cover with plastic wrap and refrigerate for at least 2 hours.
Slice bars and serve
Notes
Bars are best served fully chilled
May cut bars into mini sized bars for a dessert buffet