Preheat oven to 475°F. Oil a rimmed 13×18-inch baking sheet, spreading oil into the corners.
In a large bowl, whisk together flour, powdered milk, sugar, yeast, and salt.
Add warm water and 2 tablespoons oil. Stir until a shaggy dough forms.
Turn dough onto a lightly floured surface and knead for 3 to 4 minutes, until smooth.
Place dough on the oiled pan and press outward with fingertips. If it springs back, let it rest 5 minutes, then press again until it reaches the edges.
Cover loosely with a towel and let rise 15 minutes.
Stir together sauce ingredients until smooth. Set aside.
Bake crust for 6 minutes.
Remove crust from oven. Spread sauce evenly over the surface. Sprinkle mozzarella and cheddar over the top. Add meat or pepperoni if using.
Bake 10 to 12 minutes, until cheese is melted and edges are lightly golden.
Rest 5 minutes before slicing into squares.