Heat oil in a large pot over medium-high heat. Add the onion, garlic, jalapeno, and carrots, stirring until onion turns clear and the veggies soften. Add the seasonings and squeeze in half of the lime juice to deglaze the pot. If using beef, add it now and cook until browned. Next, add the tomatoes, black beans, and corn. Taste and add additional seasonings as needed. Bring to a boil, then reduce heat to a gentle simmer for 10-15 minutes. Just before serving, add the remaining lime juice and serve with cilantro and avocado.