1 to 2tablespoonsfresh rosemary, chopped (see notes)
Salt and freshly ground pepper to taste
Bring a pot of salted water to a boil for the tortellini.
Heat the butter and olive oil in a large pan over medium heat. Add the onions and cook until soft and translucent, 2 to 3 minutes. Add the garlic and continue cooking until fragrant, 1 minute longer.
Reduce the heat to medium-low and add the water. Cover and continue cooking, stirring occasionally, until the onions are lightly caramelized, about 5 minutes longer. If necessary, add a little more water to keep the onions from browning.
Raise the heat to medium, add the tomatoes and 1 tablespoon of the rosemary. Allow to heat through, then season to taste with salt and pepper. Taste and add more rosemary if desired. Continue cooking, stirring occasionally, for about 5 minutes. Stir in the half-and-half and keep warm.
Cook the tortellini according to the package directions. Drain and divide among 4 shallow bowls. Top with the sauce and add a bit of freshly ground black pepper and a short sprig of fresh rosemary for garnish if desired.
Tips for Making This Recipe
About the tortellini: We find that a mild-flavored, 3-cheese variety makes the best choice for this dish. Tortellini made with a single, sharp cheese tend to compete with the flavor of the rosemary in the sauce.About the rosemary: Fresh rosemary can vary in flavor intensity, so start with a tablespoon, let the sauce cook for a minute or two, then add more if desired. We used the full 2 tablespoons, but our rosemary leaves were very tender and not overly strong. If necessary, you can substitute 1 to 2 teaspoons of dried rosemary for the fresh.