Preheat and prep the squash: Heat the oven to 400°F (200°C). Carefully cut the spaghetti squash in half lengthwise and scoop out the seeds. Drizzle cut sides with 1 tablespoon olive oil, and season with salt and pepper.

Roast: Place squash halves cut-side down on a parchment-lined baking sheet. Roast for 35–45 minutes, until the flesh is tender and strands pull away easily with a fork. Time varies by size, so check at 35 minutes.

Shred the strands: When cool enough to handle, use a fork to scrape the squash into spaghetti-like strands. Leave strands inside the shells if you plan to use them as “boats,” or transfer to a bowl if baking in a casserole dish.

Sauté aromatics: In a large skillet over medium heat, add remaining 1 tablespoon olive oil. Sauté onion 3–4 minutes until softened. Add garlic and cook 30 seconds until fragrant.

Wilt the spinach: Add fresh spinach to the skillet and cook until wilted, about 2–3 minutes. If using frozen spinach, add it now and cook until warmed through. Squeeze out excess moisture if needed to avoid a watery sauce.

Add artichokes: Stir in chopped artichoke hearts and cook 1–2 minutes to warm.

Make it creamy: Reduce heat to low. Add cream cheese and heavy cream, stirring until smooth and melted. Mix in Parmesan, half of the mozzarella, lemon juice, red pepper flakes (if using), and a pinch of salt and pepper. The sauce should be thick, creamy, and coating the spoon.

Combine with squash: Add the spaghetti squash strands to the skillet and toss to coat thoroughly. Taste and adjust seasoning with more salt, pepper, or lemon as needed.

Load and top: Spoon the mixture back into the squash shells or into a greased baking dish. Sprinkle the remaining mozzarella over the top for that golden, bubbly finish.

Broil to finish: Set the oven to broil. Broil 2–4 minutes until the cheese is melted and lightly browned. Watch closely to prevent burning.

Garnish and serve: Let rest 5 minutes. Top with chopped parsley and another dusting of Parmesan if you like. Serve warm.