Sheetpan Layerless Lasagna

50min · 6 servings Ingredients: • 4 tablespoons olive oil, divided • 1/2 teaspoon kosher salt, plus more for the pasta water • 1 pound taccole pasta or lasagne pasta broken into 2-inch pieces • Notify Me • 1 clove garlic, chopped • 1/2 teaspoon red pepper flakes • 1 (5- ounce) container baby spinach • 1 cup part skim ricotta cheese • 1 pound spicy Italian sausage, casings removed • 1 red onion, diced • 4 cups jarred marinara sauce • 2 1/2 cups shredded low moisture mozzarella, divided • 1 1/2 cups freshly grated parmesan cheese, divided https://giadzy.com/blogs/recipes/sheet-pan-layerless-lasagna?_pos=1&_psq=sheetpan&_ss=e&_v=1.0