Bring a large saucepan of salted water to the boil for the ravioli (see Make it faster). Finely chop the onion. Put the walnuts in a cold medium deep frypan over medium heat. Toast, tossing, for 3-4 mins until evenly golden. Remove from the pan, reserving the pan.
Step 2 — Cook ravioli
Cook the ravioli in the pan of boiling water for 3 mins or until al dente. Reserve 125ml (½ cup) cooking water, then drain the ravioli.
Step 3 — Soften onion
Meanwhile, heat a drizzle of olive oil in the reserved pan over medium heat. Cook the onion, stirring, for 3 mins or until softened. Season with salt and pepper.
Step 4 — Simmer sauce
Add the tomato passata, reserved cooking water and 1 tsp sugar to the onion and bring to the boil. Reduce the heat to medium-high and cook, stirring occasionally, for 5 mins or until slightly thickened. While the sauce is simmering, coarsely chop the walnuts.
Step 5 — Serve up
Add the ravioli and spinach to the sauce and gently stir until the spinach is wilted and the ravioli is warmed through. Remove the pan from the heat. Taste, then season with salt and pepper. Divide the ravioli and sauce among bowls, crumble over the feta and scatter over the walnuts. Enjoy!
Step 6 — Make it faster
Speed things up by using your kettle to boil the water.