Preheat oven to 350 degrees F. Line an 8 x 8-inch square pan with parchment and spray with nonstick spray.

In large mixing bowl, whisk together flour, sugar and salt.

Add butter and use your hands to combine until mixture resembles coarse breadcrumbs.

Gently press mixture into prepared pan.

Bake 30-35 minutes, until lightly golden brown. Remove from oven and set aside. Leave oven set at 350 degrees F.

In medium bowl, whisk together eggs, egg yolks and sugar.

Whisk in flour, followed by grapefruit juice, lemon juice and grapefruit zest.

Whisk in pink food coloring, if using.

Pour grapefruit topping over warm shortbread base.

Bake 30 minutes or until center just barely jiggles.

Cool bars at room temperature for 2 hours. Transfer to refrigerator and chill for at least 2 hours or until ready to serve.

Prior to serving, dust with confectioner's sugar. Slice into 16 2-inch squares.

Refrigerate leftover bars in airtight container for up to 3 days.