Cut off the stalks of the Mexican squash, then slice off the dried tips at the opposite end without removing too much of the squash.
Using a knife or apple corer, carefully hallow out the squash and remove the flesh without puncturing the outside of the squash. You can reserve the flesh for another recipe.
Heat the olive oil in a large pan on medium heat large. Add the onions and ground beef and season with 7 Spice, 1 teaspoon salt and pepper. Cook until the beef is browned, about 7-10 minutes. Add the uncooked rice, the remaining salt and stir to combine the ingredients.
To make the tomato broth, heat the olive oil in a large deep pot over medium. Add the tomato paste and pressed garlic and season with salt and pepper. Cook until the mixture becomes fragrant, about 1 minute. Add the chicken broth and bring mixture to a boil. Lower heat to a simmer, while stuffing the squash.
Using a small spoon or your hands, fill the hallowed out inside of each squash with the rice stuffing. Be sure to leave about ¼ inch of empty space at the top since the rice will expand when cooked. Then stuff a tomato chunk on top to seal the squash and prevent the stuffing from coming out when cooked. Repeat with the remaining squash. If you have any leftover stuffing, you can cook it with water.
Transfer the stuffed squash to the deep pot and bring mixture to a boil, then lower the heat to medium and cook covered for 45 minutes. Uncover the pot, reduce the heat to low and continue cooking until the kousa is knife tender and the sauce thickens, 30-45 minutes.
Serve the stuffed squash warm with the sauce on top.