Add the onion, bell peppers, garlic, ginger, tomato paste, and all the spices to your slow cooker.
1 medium onion
1 medium red bell pepper
1 medium green bell pepper
2 large garlic cloves
1 inch piece fresh ginger
2 tablespoons tomato paste
1 tablespoon garam masala
1 teaspoon ground cumin
1 teaspoon ground coriander
½ teaspoon ground turmeric
½ teaspoon salt
¼ teaspoon ground black pepper