Preheat the oven to 375°F (190°C). Toss the cherry tomatoes with olive oil, kosher salt, and black pepper, spread on a baking sheet, and roast for 20–25 minutes until caramelized and bursting. Set aside. Meanwhile, warm the stock in a separate saucepan over medium-low heat and keep it warm throughout.

Heat olive oil in a heavy-bottomed saucepan over medium heat. Add the diced onion and cook for 3–4 minutes until softened. Stir in the minced garlic and red pepper flakes and cook for 30 seconds until fragrant.

Add the tomato paste and cook, stirring constantly, for 2 full minutes until deeply fragrant and caramelized. This step is important — don't rush it.

Add the arborio rice and stir for 1–2 minutes until lightly toasted. Pour in the white wine and stir until mostly evaporated. Stir in the crushed San Marzano tomatoes and cook for 1 minute.

Add one ladle of warm stock and stir frequently until fully absorbed. Continue adding stock one ladle at a time, allowing each addition to fully absorb before adding the next. Continue for 15–18 minutes until the rice is al dente and creamy.

Remove the pan from the heat. Stir in the roasted cherry tomatoes, Parmesan, and mascarpone until silky and combined. Add the thyme and lemon zest, taste and adjust seasoning, then spoon into bowls. Garnish with fresh basil and extra Parmesan and serve immediately.