In a food processor or blender, place spinach, basil, pepitas, 3 tablespoons of olive oil, lemon zest, lemon juice and nutritional yeast, and purée until smooth. If necessary you can add 1/4 cup water. Season with salt and pepper and set aside in a bowl. In a wide skillet, heat remaining 3 tablespoons of olive oil with garlic and crushed red pepper and sautée for 2 minutes. Add the spaghetti and water. Bring to a simmer and stir to keep pasta from sticking together. Cook until the water has reduced to a creamy consistency and pasta is al dente, about 12-15 minutes. Remove from heat and add spinach pesto. Pasta will continue to cook so make sure you remove from the heat while there is still a little bit of water yet. Adjust your seasonings with salt and pepper.