In a food processor fitted with the metal blade, chop the carrots and onions. Put them in a microwave-proof dish and cover with plastic. Microwave on high for about 2 minutes or until the vegetables are just tender. Run a bit of ice cold water over the vegetables and drain to stop the cooking process. Put the fish in the food processor. Purée until just smooth. Add eggs and ice water, kosher salt, sugar, and ground pepper. Pulse until the mixture is uniform. Add the matzo meal, horseradish, dill, and reserved vegetables. Pulse until completely mixed.
Take a tiny amount of fish mixture and cook it just until it turns color in the microwave. Then taste this tiny sample for seasoning. This is a safe method of seasoning gefilte fish, unlike our grandmothers or great grandmothers who sometimes tasted raw fish mixtures. Adjust the seasonings.
Spray a 9x5x3 inch loaf pan with vegetable oil spray. Cut some parchment paper to line the bottom. Spray the paper. Spoon the fish mixture into the pan, put the pan in a bain marie (hot water bath) in a 325° F. oven. Bake for 1 hour unti fish is firm. Remove from the oven, cool for 10 minutes, loosen from the pan with a sharp knife, and unmold unto a large dish. Cool in refrigerator, well wrapped. Serve in slices with additional horseradish.