Place the squash, cut side up on a baking sheet and bake for 40-50 minutes, or until a knife tender. Shut off the oven and leave the squash inside for 30 more minutes.
Drain and rinse the cashews and add them to a high speed blender. Add in the almond milk and blend until smooth. Transfer to a bowl and stir in the nutritional yeast, garlic, rosemary, lemon juice, salt and pepper.