Drain your black beans and discard all the juice. 

Add bacon fat or vegetable oil to a medium skillet over medium heat.

When fat is melted and shimmering, add diced onion.

Saute onions until they are becoming slightly soft. Season your onion with salt and pepper at this point.

Add minced garlic and drained black beans. Cook over medium heat, stirring occasionally for 4 to 5 minutes. 

Remove from heat and allow bean mixture to cool. Taste and add extra salt and pepper if needed. 

Add cooled bean mixture to a blender or immersion blender and blend until you get a spreadable consistency. If you do not have a blender you can use a potato masher. 

Use this as a dip for tortilla chips or a very savory spread on a sandwich.