Sautè 1 pound peeled, seeded and chopped plum tomatoes with thyme; drain. Sautè 1 pound spinach with garlic; chop and drain. Mix tomatoes with 3 eggs and 2 tablespoons cream. Mix spinach with 3 eggs and 3 tablespoons cream. Mix 3 more eggs with 3 tablespoons cream and 1/2 cup each of grated Parmesan and Gruyère. Season eggs. Bake tomato mix in a buttered 8 1/2-by-4-inch glass loaf pan in a boiling water bath at 300° for 25 minutes, until set. Top with cheese mix and bake; repeat with spinach mix. Let cool, unmold and slice.