Heat 1 tablespoon olive oil in a large skillet over medium heat. Add the chopped yellow onion and cook, stirring occasionally, until softened, about 3–5 minutes.

Add the 2 lbs lean ground beef (or turkey or chicken) and the 3 cloves minced garlic to the skillet. Use a wooden spoon to break up the meat and cook until no pink remains, about 5–8 minutes. Drain and discard the grease/liquid from the pan.

Transfer the cooked meat, onion, and garlic to a 6-quart (or larger) slow cooker.

To the slow cooker add the chopped red bell pepper (seeds removed), both cans of kidney beans (rinse and drain each 15-oz can before adding), the 15-oz can fire roasted tomatoes, the 15-oz can diced tomatoes, the two 15-oz cans tomato sauce, 1 cup beef broth, 2 to 3 tablespoons chili powder, 1 tablespoon ground cumin, 1 teaspoon paprika, 1 teaspoon kosher salt, 1/4 teaspoon cayenne pepper, and 1 tablespoon pure maple syrup (optional). Stir until ingredients are evenly combined.

Cover and cook on LOW for 6 to 8 hours or on HIGH for 3 to 4 hours.

When the chili is done cooking, remove the lid and stir in the 1/4 cup sliced tamed jalapeño peppers, if using. Taste and adjust seasoning as desired (add more chili powder, salt, or cayenne pepper if needed).

Ladle the chili into bowls and serve with your choice of toppings (shredded cheese, sour cream, sliced green onions, jalapeño slices, cilantro, avocado, etc.).