Cut the spaghetti squash in half, remove the seeds and scoop out all the stringy flesh into a bowl. (You will have approximately 5-6 cups of squash.) In medium skillet over medium heat, cook the onion in 1 tablespoon olive oil until translucent, about 4 minutes. Add the sage, rosemary and garlic, and cook until fragrant, about one minute. Remove pan from heat and cool slightly.
Place the fresh parsley and remaining 1/3 cup of olive oil in a blender and blend just until parsley is broke up. Add the cooled onion, sage and rosemary mixture, parmesan, lemon juice and pecans. Pulse until somewhat blended but not smooth. Add salt and pepper to taste and a little water if needed.