Preparation Preheat oven to 425°F with rack in middle. Butter a 3-quart baking dish (about 13 by 9 by 2 inches). Drain tomatoes, reserving 1 cup juice, then chop. Heat 2 tablespoons butter in a 5- to 6-quart heavy pot over medium-high heat until foam subsides, then cook onions with 1/2 teaspoon salt, stirring occasionally, until golden-brown, about 10 minutes. Add garlic, allspice, and cloves and cook, stirring, 1 minute. Stir in tomatoes with reserved juice, thyme, brown sugar, and 1/2 teaspoon pepper and briskly simmer, uncovered, stirring occasionally, until thickened, about 20 minutes. Meanwhile, melt remaining 1/2 stick butter and brush onto both sides of bread. Halve each slice. Transfer tomato mixture to baking dish and top with bread, overlapping slightly. Bake until bubbling and bread is crisp and golden-brown, about 20 minutes.
Preparation Preheat oven to 425°F with rack in middle. Butter a 3-quart baking dish (about 13 by 9 by 2 inches). Drain tomatoes, reserving 1 cup juice, then chop. Heat 2 tablespoons butter in a 5- to 6-quart heavy pot over medium-high heat until foam subsides, then cook onions with 1/2 teaspoon salt, stirring occasionally, until golden-brown, about 10 minutes. Add garlic, allspice, and cloves and cook, stirring, 1 minute. Stir in tomatoes with reserved juice, thyme, brown sugar, and 1/2 teaspoon pepper and briskly simmer, uncovered, stirring occasionally, until thickened, about 20 minutes. Meanwhile, melt remaining 1/2 stick butter and brush onto both sides of bread. Halve each slice. Transfer tomato mixture to baking dish and top with bread, overlapping slightly. Bake until bubbling and bread is crisp and golden-brown, about 20 minutes.