Place squash, two halves at a time (or all four if small enough), cut-side down, in a Multipurpose Steamer. Cover and microwave on high for 15 minutes. Set aside and repeat with the two other halves, if needed.
Meanwhile, preheat oven to 350° F (175° C) and prepare filling by combining beans, veggies, salsa, cheese, and seasoning.
Arrange the acorn squash halves cut-side up on a Sheet Pan lined with a Bake & Roll and divide the stuffing evenly among each.
Bake for 15 minutes or until the stuffing is heated. Remove from oven and let stand for 2–3 minutes. Garnish with Guacamole and cilantro, if desired.
Tip: Prep ahead by stuffing the squash the day before and baking to heat through right before serving.