Preheat oven to 400 degrees.

Lightly shave the center bottom of each squash half so that they can sit flat. Place the squash halves, center side down, in a casserole dish. Bake until tender, 35-40 minutes.

While the squash cooks, heat oil in a large pot with a tight-fitting lid over medium heat. Add ground beef, a few pinches of cinnamon and nutmeg, and 1 teaspoon of salt. Cook, stirring frequently, until browned and cooked through (5-10 minutes.)

Transfer the beef to a dish with a slotted spoon, leaving the cooking liquid in the pot.

Add onion to the pot and cook until slightly translucent, about 5 minutes. Add garlic and cook until fragrant, about 30 seconds. Add the remaining teaspoon of salt and the bulgur, then stir to combine.

Add water and bring to a boil. Reduce heat to medium-low, cover and simmer for about 15 minutes. Remove from heat and let sit, covered, for about 5 minutes.

Fluff the bulgur with a fork. Add the beef, raisins, parsley, and nuts.

When the squash is done, remove from the oven. Scrape out the insides to form 1/4" thick bowls. Mix the squash scrapings with the bulgur and beef mixture. Divide the mixture between the squash bowls. Return to the oven and bake until warmed through and the tops are golden (around 15 minutes.)

Serve with yogurt sauce, or as is.