In a deep 10- to 12-inch frying pan over high heat, stir oil, onion, and ginger until onion is lightly browned, about 2 minutes.
Add broth, soy sauce, and sugar. Crumble tofu into about 1-inch chunks and add to pan. Bring to a boil.
Add spinach, cover, and cook until wilted, about 1 minute. Meanwhile, in a small bowl, beat eggs to blend.
Reduce heat to low, evenly distribute mixture in pan, and pour in eggs. With a spatula, push vegetables aside slightly so egg mixture can flow down through sauce. Cover and cook just until eggs are softly set, 2 to 2 1/2 minutes.
Meanwhile, spoon rice into bowls. Top equally with egg-spinach mixture, including juices. Sprinkle with tomato.