Put a teaspoon of oil into a pan on medium-high heat and add the chard stalks. Saute for four minutes.
Add the leaves and saute until wilted and cooked - about three minutes
Transfer to a bowl and cover.
Wipe the pan clean, pour in 90 ml oil and return to heat. Add the garlic, onion, lemon peel and oregano and fry gently for 12 minutes until the onion is soft and golden.
Add the diced tomatoes, salt and pepper, and cook for about two minutes until the tomatoes soften.
Stir in the cooked chard and the olives.
Turn off the heat and leave for five minutes to allow the flavours to mix together.
Take out the oregano stalks and lemon peel and transfer the mixture to a serving dish.
Drizzle over the lemon juice and remaining olive oil, scatter the basil leaves over the top and add pepper.
Serve.