2 tablespoons olive oil
1 tablespoon finely chopped fresh sage
2 pound butternut or kabocha squash, peeled, seeded, and cut into small ½-inch pieces (about 3 cups)
1 medium yellow onion, chopped
2 garlic cloves, pressed or chopped
⅛ teaspoon red pepper flakes (up to ¼ teaspoon for spicier pasta sauce)
Sea salt and/or kosher salt
Freshly ground black pepper
2 cups vegetable broth
12 ounces whole grain linguine or fettucine
Optional additional garnishes: shaved Parmesan or Pecorino and/or smoked salt