Step 1

In a large bowl or the bowl of a stand mixer fitted with a dough hook attachment, combine the semolina flour, all-purpose flour, and salt at medium speed. Add the water and stir with a wooden spoon or mix on medium speed until a cohesive but not sticky dough forms, 1 to 2 minutes. Add more water, 1 tablespoon at a time, and knead with your hands or on medium speed until the dough is smooth and soft without being sticky or dry, about 8 minutes more. Cover the dough with plastic wrap and let rest at room temperature for 1 hour.

Step 2

Line two baking sheets with parchment paper and dust with semolina flour. With a rolling pin, roll the dough on an unfloured work surface into a flat sheet ¹⁄8 inch (4 mm) thick, and then cut into ¹⁄8-inch- (4-mm-) wide strips. With your hands, roll one strip back and forth on the work surface into a fat spaghetti-like strand. Put the pici on the prepared baking sheets and shape the remaining dough. Make sure that the pici don’t touch or they will stick together. (To store, refrigerate on the baking sheets, covered with plastic wrap, for up to 2 days, or freeze on the baking sheets and transfer to an airtight container. Use within 1 month. Do not thaw before cooking.)

Step 3

In a medium pot, warm the olive oil over medium heat. Add the garlic, onion, rosemary, bay leaf, and red pepper flakes and cook until the onion is translucent, about 10 minutes. If the onion begins to brown, lower the heat. Add the tomatoes and butter and simmer, stirring occasionally, until the sauce is slightly thick and soft but not pasty, about 45 minutes. The butter should emulsify into the sauce. Season with salt. Set a fine-mesh strainer over a large bowl and pour the sauce into the strainer. Discard the solids in the strainer. (To store, transfer to an airtight container and refrigerate for up to 2 days, or freeze for up to 1 month. To thaw, place in the refrigerator overnight or until fully thawed.)

Step 4

Bring a large pot filled with generously salted water to a simmer over medium-high heat. Add the pici and simmer until they float to the surface, 1 to 3 minutes. Simmer until slightly al dente, 1 to 2 minutes more. Remove immediately with tongs and finish with tomato sauce.

Step 5

For each serving, warm about ½ cup (120 ml) of the tomato sauce in a sauté pan over medium heat. Add 1 ½ teaspoons to 1 tablespoon butter per serving, depending on how naughty you feel, and gently simmer until the bubbles get large and the sauce is not watery along the edges of the pan. The sauce should be thick and silky, not dry or pasty. Add the cooked pici and simmer for 1 minute to let them absorb the flavor of the sauce. Spoon into serving bowls and top with grated Parmigiano-Reggiano. Serve right away.