Heat olive oil in a large Dutch oven or soup pot over medium high heat. Add onion and red pepper and sauté until tender, about 4 minutes. Add the garlic and tomato paste, cook for two 2 minutes.
Stir in vegetable broth, diced tomatoes, tomato sauce, red beans, black beans, chili powder and cumin. Season with salt and pepper, to taste.
Add the uncooked macaroni and stir to combine. Place a lid on the pot and turn the heat up to medium high and bring to a boil. Stir often to loosen the noodles from the bottom of the pan. When it reaches a boil, reduce to low and simmer until the pasta is cooked, about 12-15 minutes.
Remove from heat and remove the lid. Stir in 1/2 cup of the shredded cheddar cheese. Top with remaining 1/2 cup cheese and place the lid on until cheese is melted. Garnish with green onions, if desired. Serve immediately.