Step 1

Preheat oven to 350 degrees.  Spray a 13 x 9 casserole dish with cooking spray.

Step 2

Cook pasta according to package directions, adding vegetables in the last two minutes. Drain and rinse with cool water.

Step 3

Meanwhile, make sauce by melting butter in a saucepan over medium heat.

Step 4

Add flour and whisk for 2 minutes, until golden brown. (Note that some gluten-free flours do in brown well.)

Step 5

Add milk and cook until slightly thickened, about 8 minutes, stirring often. Add all but 1/2 cup cheese, mustard powder, salt, pepper and cayenne.

Step 6

Cook over low heat until cheese melts.

Step 7

Toss pasta and veggies with cheese sauce and place in a casserole dish. Top with remaining cheese.

Step 8

Bake for 25 minutes.