Preheat oven to 400 degrees. While the water boils for the macaroni, prepare the vegetable puree. Bake or steam vegetable of choice until tender. A fork should pierce the flesh and slide out easily.
Once the veggies are cooked, puree in a food processor with fresh water until smooth.
Cook macaroni until al dente, do not overcook. Drain and set aside in a small bowl.
Coat the bottom of a medium baking dish with oil. Place a layer of macaroni mixed with vegetable puree on the bottom of the dish, just enough to cover.
Sprinkle with a little black pepper before covering with shredded cheddar. Add another layer of noodles, puree, pepper, then cheese.
Finish by drizzling milk over everything. Bake at 400 until bubbly and the top just starts to brown and crisp, about 40 minutes.