Preheat your oven to 400 degrees F. Spray a 13x5-inch tart pan with nonstick spray. Set aside.

In a medium size mixing bowl, combine the finely ground pretzels, melted butter, and sugar. Stir until the pretzels are “wet.”

Pour the pretzel mixture into the tart pan and press firmly down to create the crust.

Bake the crust for 6 to 8 minutes.

Remove from oven and allow to cool at room temperature.

In a medium saucepan, combine the sugar, milk, corn starch, lemon juice, and lemon zest. Cook over medium heat, stirring frequently, until mixture thickens - about 6 to 8 minutes. The mixture should be able to coat a spoon. Reduce heat to low.

In a small mixing bowl, stir the egg yolks. While stirring the egg yolks, slowly add two tablespoons of the lemon mixture to the egg yolks. Once the lemon mixture is added, slowly add two more tablespoons of the lemon mixture to the egg mixture. This will temper the egg yolks so they don’t cook when you add them to the lemon mixture.

Once the egg yolks are tempered, slowly add the yolk mixture into the lemon mixture, stirring constantly.

Continue to cook on medium heat for about 3 minutes.

Remove from heat and allow to cool completely.

Stir in the sour cream.

Pour the lemon filling onto the pretzel crust. Refrigerate overnight.

Top with whipped cream when ready to serve.

In a stainless steel bowl, combine the whipped cream, powdered sugar, and lemon extract. Beat on high speed until stiff peaks form.