Preheat oven to 425° F.
Melt 2 Tbsp butter in a skillet and sauté chopped onion and chopped red bell pepper until soft; set aside.
In a large bowl mix together flour, baking powder, salt, white pepper, and cayenne pepper. Cut in 4 Tbsp butter until coarse crumbs are formed. Stir in Gruyere cheese, cheddar cheese, the onion mixture, and milk; stir just to blend.
On a lightly floured flat surface, form the dough into 12 rounds, flatten, and place on a greased baking sheet. Brush with milk. Bake for 15 minutes.Servings: 12 scones