"I made this up as a way to use a squash and some leftover couscous. It looks awful, but it tastes really good! It has a nice flavor my wife called sweet and gentle. Serve in bowls over rice or couscous."
Place acorn squash cut-side down in a glass baking dish. Pierce the skin in a few places with a sharp knife. Pour in 1 inch water.
Cook squash in the microwave on high until tender, 10 to 15 minutes. Cool until easily handled, about 5 minutes. Scoop flesh into a large bowl; discard skin.
Preheat a large, heavy skillet over medium heat. Add olive oil. Add onion and garlic; cook and stir until onion is translucent, 4 to 5 minutes. Stir in diced tomatoes with their liquid; simmer until softened, 3 to 5 minutes. Stir in mushrooms; cook until softened, about 2 minutes.
Stir squash gradually into the skillet. Pour in red wine, stirring to loosen mixture. Add basil. Simmer, stirring occasionally, about 2 minutes. Spread spinach on top. Cover skillet; cook until wilted, 3 to 5 minutes. Stir spinach into the mixture. Season with salt and pepper.