To make the slow-roasted tomatoes, preheat the oven to 275°F (135°C). Cut 2–3 cups of baby tomatoes in half and arrange them cut side up on a lightly oiled baking tray. Lightly sprinkle with salt and pepper, then roast for 2–3 hours until the tomatoes become jammy, soft, and slightly dried, resembling sun-dried tomatoes.
While the tomatoes roast, prep the ingredients for the sauce: chop the red onion, mince the garlic, and finely chop the sun-dried tomatoes.
Heat the sun-dried tomato oil in a large pan over medium heat for about 1 minute. Add the chopped red onion and sauté for 4–5 minutes until soft and translucent.
Stir in the minced garlic, chopped sun-dried tomatoes, and red pepper flakes, cooking for another minute until fragrant.
Add the tomato paste and cook for 3–5 minutes, stirring frequently. Sprinkle in the flour and cook for 1–2 minutes, stirring often.
Slowly whisk in the chicken broth and heavy cream until smooth. Season with oregano, smoked paprika, black pepper, and salt. Stir and let the sauce simmer on medium heat for 5–10 minutes until it deepens in color and thickens slightly.
Meanwhile, cook your pasta according to package instructions, but drain it about 1 minute before it reaches al dente. Reserve 1 cup of pasta water before draining.
Add the spinach, the slow-roasted tomatoes (from step 1), and a squeeze of lemon juice to the sauce along with the al dente pasta and a splash of the reserved pasta water. Simmer together on medium heat for 2–3 minutes until the pasta is cooked perfectly and the sauce thickens slightly.
Turn off the heat and stir in the grated Pecorino Romano. Add in fresh basil and stir well to combine.
If needed, slowly stream in reserved pasta water to loosen the sauce and make it extra creamy before serving.
