In a large measuring glass or blender canister, combine the avocado, sour cream, lime juice, salt, garlic, and cilantro. Use an immersion blender or canister blender to blend until it is mostly smooth, one minute.
1 ripe avocado, ⅓ cup sour cream (or Greek yogurt), ⅓ cup fresh lime juice, 1 tsp kosher salt, 1 clove garlic, ¼ cup chopped fresh cilantro