1 medium spaghetti squash (about 2.5–3 pounds)
2 tablespoons olive oil, divided
1.25–1.5 pounds steak (ribeye, New York strip, or sirloin), about 1-inch thick
1.5 teaspoons kosher salt, divided (plus more to taste)
3/4 teaspoon black pepper, divided
5 tablespoons unsalted butter
4 cloves garlic, finely minced
1 teaspoon Italian seasoning or a mix of dried parsley, oregano, and thyme
1/4 teaspoon red pepper flakes (optional, for heat)
1 tablespoon fresh lemon juice, plus more to taste
2 tablespoons chopped fresh parsley (or chives)
Grated Parmesan or shaved Asiago for serving (optional, but delicious)