Preheat the oven to 300°F. In a small bowl, toss together the tomatoes, vinegar, olive oil, sugar, salt, and pepper.

Line a rimmed baking sheet with foil and place the tomato mixture on the baking sheet.

Bake until the tomatoes just begin to burst, about 30-35 minutes. Toss the mixture once halfway through the baking process. When most of the tomatoes look to have burst, remove the baking sheet from the oven and allow them to cool slightly.

Gently toast the baguette slices under a broiler in the oven for about 1 minute. Watch closely, as they can burn quickly. Once toasted, top each baguette slice with about 2 teaspoons ricotta, a spoonful of the tomato mixture, and some slivered basil.

Lightly drizzle any remaining vinegar and olive oil from the sheet pan over the prepared crostini. Serve immediately.