Heat 1 tablespoon of the oil in a large nonstick frying pan. Add the chorizo and cook for 2 minutes until golden, then remove from the pan and set aside.
Add the onion to the pan and cook for 3 minutes until starting to soften, then add the sweet potatoes. Cook gently for a further 10 minutes until the sweet potatoes are tender, then season to taste. Return the chorizo to the pan and heat through.
Mix the pesto with the lemon juice and capers. Serve the rocket with the sweet potato hash and drizzle over the pesto.