Press garlic through a garlic press and put it in a jar or cup. Add the lime zest, juice, and minced green onion or shallot, and minced chili.
Toast the cumin and coriander seeds in a small dry skillet until fragrant, then transfer to a plate to cool. Grind in a spice grinder or with a small mortar and pestle, then add to juice mixture.
Whisk in the oil and mustard and add the chopped cilantro and let stand at least 15 minutes before using.
For a quicker preparation and slightly more emulsified dressing, toss all ingredients (roughly chopped) into a blender and pulse to combine.