1/2 recipe Walnut-Pecan Shortbread dough (
click here)
4 egg yolks
1/2 cup sugar
3 tablespoons flour
2 teaspoons finely minced lime zest
2 teaspoons finely minced grapefruit zest
2/3 cup fresh grapefruit juice
1/2 cup fresh lime juice
1 to 2 tablespoons butter
1 cup pink grapefruit sections, cut in half