Preheat and prep. Heat the oven to 400°F (200°C).
Line a baking sheet with parchment for easy cleanup. Carefully halve the spaghetti squash lengthwise and scoop out the seeds.
Season the squash. Rub the cut sides with about 1 tablespoon olive oil. Season generously with salt and pepper.
Place cut side down on the baking sheet.
Roast until tender. Bake for 35–45 minutes, depending on size, until the flesh is easily pierced with a fork and strands pull apart. The edges should be lightly caramelized for the best flavor.
Make the tomato topping. While the squash roasts, warm 1 tablespoon olive oil in a large skillet over medium heat. Add garlic and red pepper flakes.
Cook 30–60 seconds, just until fragrant.
Cook the tomatoes. Add the tomatoes, oregano, a pinch of salt, and black pepper. Cook 4–6 minutes, stirring occasionally, until the tomatoes soften and release some juices but still hold their shape. Turn off the heat and stir in lemon juice if using.
Shred the squash. When the squash is cool enough to handle, flip the halves and use a fork to pull the strands into “spaghetti.” Leave the strands in the shells or transfer to a serving bowl.
Combine. Pour the warm tomato mixture over the squash.
Sprinkle with feta and chopped herbs. Toss gently to combine, tasting and adjusting salt, pepper, and lemon.
Finish and serve. Drizzle with a little extra-virgin olive oil. For extra texture, add toasted pine nuts or a very light drizzle of balsamic glaze.
Serve warm or at room temperature.