Slow Cooker Lentil Chili with Black Beans

In a 6 to 8 quart slow cooker, combine Red Onion (1) , Garlic (4 cloves) , Chili Powder (1 Tbsp) , Ground Cumin (1 tsp) , Smoked Paprika (1 tsp) , Sea Salt (1/2 Tbsp) , Diced Tomatoes (2 cans) , Brown Lentils (1 cup) , Canned Black Beans (1 can) , Unsweetened Pumpkin Purée (1 can) , Kale (1 bunch) , and Vegetable Stock (4 cups) .