Preheat oven to 350 degrees. Soften butternut squash in microwave. (Place in bowl with a bit of water and heat for about 3 minutes, stirring halfway through.) Place softened squash in food processor fitted with metal blade and process until chopped. Add sugar, soy milk, flour, eggs and vanilla and process until a smooth liquid. There will still be some small chunks.
Pour into 9-by-13 pan sprayed with nonstick spray. Sprinkle cinnamon on top. Bake for 1 hour or until center is firm.