Preheat oven to 300F.

Cut an X in bottom of each tomato.

Blanch tomatoes in boiling water for 10 seconds.

Transfer tomatoes to ice water to cool.

Peel off tomato skin.

Cut two thirds of tomatoes into quarters.

Arrange tomatoes, cut sides down, in a lightly oiled baking pan.

Sprinkle with half of garlic and 1/2 teaspoon thyme.

Roast until tomatoes are caramelized, about 3 hours.

Seed remaining tomatoes and finely chop.

Cook onion and remaining garlic in olive oil over low heat until soft and golden, about 20 minutes.

Add chopped tomatoes, bay leaf, and remaining thyme.

Cook, covered, stirring occasionally, until all moisture has evaporated, about 2 hours.

Drain tomato sauce in a fine-mesh sieve.

Discard liquid.

Discard bay leaf.

Macerate raisins in rum for 30 minutes.

Bring rice and water to a boil, then reduce heat and simmer, covered, until water is absorbed, about 15 minutes.

Remove from heat and let rice stand, covered, for 10 minutes.

Transfer rice to a bowl and sprinkle with vinegar.

Toss rice gently with a fork and cool.

Stir in tomato sauce, raisins (with any liquid), pine nuts, and mint.

Add salt and pepper to taste and a pinch of sugar.

Scoop rice mixture into ice cream scoop, packing it.

Release "sushi" onto a platter.

Top each piece with a roasted tomato, smooth side up.

Lightly brush with oil and dust with cumin.