Chili Mac & Cheese

In a large pot over medium heat, heat oil. Add onion and cook until tender, then add garlic and stir until fragrant, 1 minute. Add ground beef and cook until no longer pink, about 5 minutes. Drain fat. Return pot to heat and add diced tomatoes, kidney beans, chili powder, cumin, cayenne, chicken broth, and pasta and bring to a simmer. Simmer until pasta is al dente, 14 to 15 minutes. Remove from heat and stir in cheddar until just melted. Garnish with chives and serve.