Bring a large saucepan of salted water to the boil for the pasta. Finely chop the onion. Thinly slice the garlic. Coarsely chop the tomato. Coarsely chop the parsley leaves, discarding the stems.
Step 2 — Cook prawns
Heat 2 tsp olive oil in a medium deep frypan over medium-high heat. Add the prawns, season with salt and pepper and cook, stirring, for 2-3 mins until almost cooked through. Remove from the pan.
Step 3 — Start sauce
Heat 2 tsp olive oil in the same pan over medium-high heat. Cook the onion and garlic, stirring regularly, for 2-3 mins until softened. Add the tomato and cook, stirring, for 2 mins or until softened.
Step 4 — Cook pasta
FRESH FETTUCCINE OPTION Add the pasta to the pan of boiling water and cook, stirring to separate the strands, for 3-4 mins until al dente. Reserve 60ml (¼ cup) cooking water, then drain the pasta.
Step 5 — Finish sauce
Meanwhile, add the tomato paste, Tuscan seasoning and ½ tsp chilli flakes* to the tomato mixture (if preferred, omit the chilli when cooking and serve it at the table). Cook, stirring, for 1-2 mins until fragrant. Reduce the heat to medium, add the reserved cooking water, 1 tsp sugar and ½ tsp red wine vinegar and cook, stirring, for 2 mins or until slightly thickened.
Step 6 — Toss pasta and serve
Taste the sauce, then season with salt and pepper. Add the prawns and pasta to the sauce and cook, tossing, until combined and heated through. Add the spinach and toss until slightly wilted. Divide the pasta among bowls. Scatter over the parsley to serve.