Preheat the oven to 325°F and line a 9×13 pan with parchment paper.

In the bowl of a hand or stand mixer fitted with the paddle attachment add the 1 cup softened butter, and 1/2 cup confectioners sugar. Mix on low speed moving up to medium to cream until combined, about 2 mins. Add the 2 cups all purpose flour, 1/4 tsp kosher salt, and zest of 1 lemon, and mix again on low until the dough starts coming together in a ball.

Stop the mixer and press the dough together into one smooth ball. Drop the ball of dough into the lined 9×13 pan and press and spread out evenly into the pan.

Bake for 20 minutes. Remove, raise the oven temperature to 350°F, and let cool.

Meanwhile make the crumb topping. In a small bowl combine the 1 cup flour, 1/2 cup brown sugar, 1/4 cup white sugar, 1/4 tsp cinnamon, 1/4 tsp kosher salt, 1/2 cup cold diced butter, and zest of 1 lemon.

Using your fingers, mix and pinch the butter into the mixture gently until small clumps form and are about the size of a pea. Put the bowl in the freezer while the crust continues baking.

Toss the raspberries in a medium bowl with 2 tbsp flour, 2 tbsp lemon juice, and 1/4 cup sugar. When the crust is cooled, pour the raspberries over the crust, then sprinkle all over with the crumble.

Bake for 30 mins.

Cool on the counter for 20 minutes, then move to the fridge to chill for at least an hour but can even be overnight.

In a pourable measuring cup, add 1 cup powdered sugar, lemon zest if you're using it, and 2-3 tablespoons lemon juice. Mix and pour over the cooled bars. Using a large sharp knife, cut into 16 squares.