Quinoa and Bean Pilaf

Name: Quinoa and Bean Pilaf
Ingredients: 2 tablespoons extra-virgin olive oil; 2 bell peppers (1 red, 1 green), cut into 1/2-inch pieces; 3 scallions, sliced (white and green parts separated); 2 stalks celery, diced; 2 cloves garlic, finely chopped; 2 tablespoons tomato paste; Pinch of cayenne pepper; Kosher salt; 1 cup quinoa; 2 15-ounce cans black and/or kidney beans, drained and rinsed; 4 cups baby spinach (about 3 ounces); 1/2 cup shredded cheddar or pepper jack cheese; Hot sauce, for serving (optional)