Place a skillet over medium-high heat.
Add the olive oil. Once the oil is hot, add the bell pepper, onion, and jalapeño. Sauté the mixture, stirring often, for around 5 minutes or just until onions begin to brown. Add the garlic and continue to saute and stir for 30 seconds.
Transfer mixture to the slow cooker.
Add in the lentils, crushed tomatoes, vegetable broth, black beans, and all of the spices.
Stir to combine all of the ingredients. Cover and cook on high for 3 to 4 hours or on low for 7 to 8 hours. During the last 20 minutes of cooking, stir in the corn.
Serve the soup with your favorite toppings!