Combine the water and tomatoes in a small saucepan over medium heat; cook until the water is absorbed.
Mix together the tomatoes, ground beef, onion, bread crumbs, half-and-half, salt, and pepper in a bowl. Form the mixture into golf ball-sized spheres.
Heat the olive oil in a skillet over medium heat. Cook the meatballs in the heated oil until no longer pink in the center, turning several times to maintain even coloring; remove and set aside, reserving drippings in the skillet. Stir the water and cornstarch together to dissolve cornstarch, then mix into the drippings. Replace skillet over medium heat, bring to a boil and stir until thickened; serve on side of meatballs.
