In a bowl, mix flour, 1/4 cup granulated sugar, the brown sugar, almonds, lemon peel, 1/2 teaspoon cinnamon, and the salt. With a mixer fitted with a paddle attachment, at low speed, or with your fingers, beat or rub in butter until mixture forms coarse crumbs and begins to come together.
In large bowl, mix rhubarb, remaining 3/4 cup granulated sugar, and remaining 1/4 teaspoon cinnamon. Pour into an 8-inch square baking pan and spread level. Sprinkle evenly with flour mixture.
Bake in a 375° regular or convection oven until juices are bubbly and topping is golden brown, 45 to 50 minutes (40 to 45 minutes in convection oven).