Mince the garlic or use a garlic press, roughly chop the cilantro and juice the limes. You can also make this without a blender, just chop the cilantro and garlic finely.
Place everything but the oil into the blender and blend on low speeds to combine. Then with the motor running on low speeds, add the oil in a thin steady drizzle through the hole in the top of the lid.
Try this Cilantro Lime Dressing with my Fish Taco Bowls which you'll find linked in the recipe. It's also great as a dressing for slaw or as a marinade for chicken.