Rinse the cilantro under cold water. Shake off excess water, then dry it with a paper towel or in a salad spinner. Remove the thick lower stems, but keep the tender upper stems and leaves. Dry cilantro helps the dressing stay thicker.

Pour lime juice, vinegar, and oil into the blender first, which helps pull the other ingredients down toward the blades for a smoother blend.

Next, add mayonnaise, sour cream, garlic, jalapeño, onion powder, cumin, and salt. Place the cilantro on top. This order helps everything blend evenly. Start the blender on low for about five seconds, then switch to high. Blend for 30 to 45 seconds until the dressing is smooth and pale green.

Taste the dressing and adjust if needed. If it tastes flat, add a pinch of salt. If it needs more brightness, add a splash of lime juice. If it’s too thick, add water one tablespoon at a time. Pour the dressing into a glass jar and refrigerate for at least 20 to 30 minutes before serving.

This chilling lets the flavors blend and reduces the strong garlic taste. The dressing tastes better when cold.