Put the lemon juice, vinegar, garlic, onions, salt and pepper to taste in a large bowl. Set aside for 5 minutes. In a small skillet, toast the cumin seeds until fragrant, about 3 minutes. Grind in a spice grinder until fine. Add the honey, ground cumin, paprika and cayenne to the bowl. Whisk in the olive oil in a thin stream.
Add the carrots, beets and cilantro to the dressing. Toss. Taste and add more salt and pepper if desired.