Heat oil in a large deep skillet. While the oil is heating dice the onion and press the garlic with a garlic press or mince by hand. Add onions to the pan and saute for 10 minutes stiring often to make sure they don't burn. Once translucent add the garlic and cumin to and saute for another 5 minutes. Lower the heat so the garlic does not burn.
Add the beans and liquid and stir. Simmer uncovered for about 25 minutes or until 1/3rd of the cooking liquid evaporates. Transfer to a food blender and process until smooth. Season to taste with lemon juice and salt.
Notes
Recipe VariationsSpicy - If you want to add a kick to your beans add in 1/4 tsp of chili powder.Smokey - Add an extra tablespoon of cumin.Chunky - Remove 1/2 cup of the black beans after you cook them. Blend the rest in the food processor and then swirl the unblended beans in.Storage - You can keep this dip in the fridge for up to ten days and in the freezer for up to six months.