In a bowl, combine grated carrots, chopped onions and stir in salt and sugar. Set aside for 20 minutes then take vegetables in your hands and squeeze out the water.
Once water is drained from carrots and onions, add tuna, olive oil from the tuna can, greek yogurt, dijon mustard and citrus juice to the bowl and toss everything together.
Chill salad in the fridge or serve at room temperature. To serve, add fresh ground pepper and oven dried carrot greens as garnish.