Heat the olive oil into a cast-iron skillet and the onions.
Sautee until translucent, then add the spinach.
Saute over low heat until all the liquid evaporates.
Add the zucchini noodles and cook for 5-7 minutes, stirring frequently.
Turn of the heat and set aside.
Add the avocado, crushed nuts, basil, garlic, lemon juice and salt into the food processor and pulse to obtain a creamy pesto.
Transfer the pesto into the zucchini skillet, season with freshly ground black pepper and mix to combine.
Serve warm, garnished with crushed toasted nuts.