1.Bring a saucepan full of water to the boil. Add spinach and cook very quickly – only about 2 minutes.
2.Drain the spinach into a colander. Squeeze out the excess water from the spinach using kitchen tongs.
3.Place the drained spinach into a heatproof glass bowl.
4.Steam the zucchini until just cooked and add to the bowl of spinach.
5.Slice onions crosswise (half crescents). Heat the olive oil in a saucepan and add the onions. Cook until translucent.
6.Add the peeled, sliced tomatoes and cook for a few minutes.
7.Pour the onion / tomato / oil mix over the green vegetables, sprinkle over some sea salt and stir gently to combine.
8.Top with an extra drizzle of olive oil and serve immediately.