In a medium to large pot over medium heat, simmer the onion, garlic, celery, bell pepper, fresh tomatoes, canned tomatoes, cumin, and oregano for 10 minutes. Add half of the mixture to a high-speed blender, blend until smooth, and return to the pot.
Add the lentils, kidney beans, navy beans, sweet potatoes, paprika, chili powder, salt, pepper, and 2 cups filtered water. Bring to a boil, reduce to medium-low heat, and cook covered for about 20 minutes, or until lentils and sweet potatoes are fork-tender.
Add the sweet corn and kale and cook for another 2 to 3 minutes, or until the kale turns dark green.
Serve with sliced avocado on top! Leftovers keep best in an airtight container in the refrigerator for up to 3 days.