Thoroughly wash the swiss chard. Remove the stems and tear the remaining leaves into bite-sized pieces. Steam the chard and the onions in a large pot or wok with only the water that remained on the leaves from the washing.
When the chard has collapsed, add the tomatoes, olive oil, vinegar, garlic and shallots. Continue to steam for 5-8 minutes.
Add the beans with their liquid and season to taste. Serve with bread and thin slices of pecorino romano cheese.