Step 1

Preheat oven to 400 degrees F.

Step 2

Whisk together dry ingredients (through salt) in a medium mixing bowl.

Step 3

Add chilled butter and cut into dry ingredients, then mix in egg, egg whites, lemon, and vanilla. Dough should be thick enough to roll into a ball (add 1-2 tablespoons of gluten-free flour if dough is too sticky to handle).

Step 4

Fold in blueberries gently so they don't bleed into the dough too much.

Step 5

Lightly coat a 8" to 9" baking pan with buttery spread, or line with parchment paper.

Step 6

Form dough into a 7" circle inside pan, then use a knife to slice into eighths, pushing segments apart slightly.

Step 7

Bake for 12-15 minutes in preheated oven until edges are firm.

Step 8

Let cool for 5-10 minutes, then combine icing ingredients and drizzle over top. Enjoy!