1. In a large bowl, combine matzo meal, salt, and sugar. Set aside.
2. Separate egg whites and yolks. Beat egg yolks, and combine with water. Add the yolk mixture to the matzo meal mixture, and let it stand for 30 minutes.
3. Beat egg whites with an electric mixer until they are stiff, and fold them into the matzo meal mixture. Add grated onion, zucchini, broccoli, spinach, carrots, scallions, and sun-dried tomatoes if you’re using them.
4. Heat corn oil until it sizzles in a deep skillet. Lower heat, and, using a cooking spoon, spoon batter into the pan, creating thin pancakes 3 to 4 inches in diameter. Fry for several minutes, turning when the pancake is firm and the bottom side is golden brown. Turn and fry for another few minutes until the other side is done. Drain on paper towel. Serve with sour cream.
Use your food processor to chop zucchini, broccoli, carrots, and scallions to correct size (1⁄8-inch pebbles), to grate onions, and to finely chop spinach.
For a little extra color and tang, throw in 5 or 6 finely chopped sun-dried tomatoes (drain them first thoroughly if they’re in oil).
Occasionally stir mixture left in the bowl during the process of spooning latkes into the pan.