Roasted Tomato Soup with Mascarpone

2 1/2 lb. plum tomatoes, halved lengthwise (I often also use cherry tomatoes)
1 1/4 tsp. kosher salt, plus more, to taste
Freshly ground pepper, to taste
1 tsp. extra-virgin olive oil
1 small white onion, chopped
2 small garlic cloves, minced
1 cup water
Mascarpone Cheese
Smoked Sea salt (optional)

Preheat an oven to 425°F. Cover 1 large or 2 medium baking sheets with aluminum foil.

Arrange the tomatoes, cut sides up, on the prepared baking sheets. Sprinkle evenly with 1 tsp. of the salt and several grinds of pepper. Roast the tomatoes in the oven until they are soft but still hold their shape, about 30 minutes. (Less for smaller tomatoes).

In a heavy saucepan over medium-high heat, warm the olive oil. Add the onion and garlic and sauté until translucent, about 3 minutes. Reduce the heat to low, cover and cook until the onion releases its juices, about 6-8 minutes. Increase the heat back to medium-high and add the roasted tomatoes, along with any juices collected on the pan(s), then pour in the water. Reduce the heat to medium-low, cover and simmer until the vegetables are very soft, about 25 minutes.

Using a stick blender, blend the soup to your desired consistency. (If you don't have a stick blender you can do this in your blender: Allow soup to cool and do it in batches).

Divide the soup among warmed soup bowls and place 1 tsp. Mascarpone cheese in the center of each bowl, swirling it slightly. Garnish each with a sprinkle of smoked seasalt. Serves 4.