Step 1

Heat a Dutch oven or large, shallow pot over medium heat until hot, about 3 minutes. Add the oil, followed by the onion, and cook, stirring, until softened, 2 to 3 minutes. Add the tomato paste and cook, stirring constantly, until the tomato paste becomes darker, thicker and starts to stick to the bottom of the pot, 4 to 5 minutes. Add the garlic, 1/2 teaspoon of salt and the sugar and stir until fragrant, 15 to 30 seconds. Add the broth or water, increase the heat to medium-high and bring to a boil, stirring well to dissolve the tomato paste into the liquid.

Step 2

Add the pasta and stir to prevent sticking. Cover, reduce the heat to medium and cook for 10 minutes before tasting to see if the pasta is al dente – different brands and shapes of pasta will have different cooking times. If the pan looks dry, add a touch more broth or water. The sauce should “hug” the pasta without being overly saucy.

Step 3

Once the pasta is al dente, add the spinach, drizzle with more olive oil and season with the remaining 1/2 teaspoon of salt and a generous amount of black pepper. Taste, and adjust the seasonings, if desired. Cook, stirring, until the greens are just wilted, 1 to 2 minutes.

Step 4

Turn off the heat and stir in the tomatoes and basil until combined. Have one final taste, adjusting salt and/or pepper, if necessary.

Step 5

Divide among bowls, scatter over the crushed red pepper flakes and serve.