You could also use cauliflower.
Adapted from Living magazine
4 T. butter (or Earth Balance)
8 oz. wide noodles
Salt and pepper
1 lb. broccoli broken into 1-inch florets (about 4 c.)
1 ¼ c. yellow onion, finely chopped
2 stalks celery, cut at an angle into 1/8-inch slices (about 1 c.)
5 T. flour
2 c. milk or non-dairy substitute
2 cans tuna in water, drained and flaked
½ t. hot sauce, such as Tabasco (optional)
¼ c. parsley leaves, chopped
Preheat oven to 375 degrees. Grease a 2 1/2 –quart casserole dish. Cook pasta in a large pot of salted water 4 minutes. Add broccoli; cook until just tender, 3-4 minutes more. Reserve ½ c. water; drain pasta mixture. In same pot, melt butter or butter substitute over medium heat. Add onion and celery, season with salt, and cook until onion is softened, about 8 minutes. Add flour; cook, stirring, 2 minutes. Slowly stir in milk or substitute until mixture is thickened, about 3 minutes. Remove from heat; stir in pasta mixture, tuna and hot sauce if using. Season with salt and pepper. If too thick, add reserved pasta water. Transfer to prepared dish; cover with foil. Bake 15 minutes. Uncover, increase heat to 425 degrees, and bake until lightly browned, 10-12 minutes. Top with parsley.