Preheat oven to 400F. Spread acorn squash on a baking sheet. Toss with avocado oil, salt and pepper. Arrange in a single layer. Roast for 30 minutes, flipping half way through. While the acorn squash is roasting, prepare the pomegranate glaze. Add pomegranate juice, tamari, brown sugar, ginger, and garlic powder to a small saucepan over medium heat. Heat until it begins to boil, about 5 minutes. In a small bowl, combine water and cornstarch and stir until combined. Pour cornstarch slurry into the pomegranate juice mixture and whisk to combine. Continue whisking for 1-2 minutes, until the mixture thickens. Remove from heat.