Preheat oven to 400 degrees F. Remove stems from the squashes and cut in half lengthwise. Remove the seeds.
Brush the cut side of each squash half with a little bit of olive oil. Place squash cut side down on a baking sheet lined with parchment paper or sprayed with oil. Bake for 30-35 minutes or until tender.
While the squash is roasting, prepare the stuffing. Bring lentils and water (or stock) to a boil in a small saucepan, then cover and simmer for 20-30 minutes until tender. Drain excess water. In a small skillet, heat olive oil over medium heat. Add garlic and onion and saute for 3-5 minutes until tender.
Combine lentils, onion, and garlic in a small bowl. Add feta and dried cranberries. Mix until well combined. Add salt and pepper to taste.
Fill each acorn squash with stuffing. Top with chopped fresh sage if desired. Serve warm and enjoy!
Prep ahead: You can make this for a holiday dinner by preparing the filling ahead of time, storing in the fridge, and reheating later. You can also slice and prepare the squash in advance, and pop them in the oven later when you are ready to roast them.Make vegan: Remove the feta cheese to make these vegan.Storage: These are best consumed immediately after making, but leftovers can be stored for 1-2 days in an airtight container in the fridge.