Add 1 cup sour cream, 2 tbsp lime juice, 1 tsp lime zest, ½ tsp garlic powder, ¼ cup fresh cilantro and 1 pinch salt to a large mason jar. Blend with an immersion blender until smooth and bright green.
Taste and adjust salt or lime juice if needed.
Thin with a splash of water if you want a drizzle consistency.
Notes
Zest the lime before juicing it. It's much easier to zest a whole lime than one that's already been squeezed.
Start with less cilantro if you're unsure. You can always blend in a little more after tasting, but you can't take it back out.
Use a tall container for blending. This helps keep splatters contained while giving the immersion blender room to work.