1. In a cast-iron or other skillet, brown the sausages all over in olive oil. Set aside.
2. Peel onion and garlic cloves. Cut onion into about 8 sections, and add with the garlic to the pan in which you cooked the sausages.
3. Allow onions and garlic to cook over medium heat until quite soft, about 15 minutes.
4. Add the tomatoes to the pan with the onions and the garlic. Stir everything around, tuck the lemon slices around the sides of the pan, add about 1/2 cup of water, then allow to cook over medium heat for another 20-30 minutes. Add an additional 1/2 cup of water if the pan becomes too dry (if using the canned tomatoes, you can use the tomato liquid instead of water).
5. Slice up the cooked sausages and add with the chard to the pan, stir everything around, and simmer for about 5 more minutes.
6. Crack eggs over the contents of the skillet. Cover and keep over very low heat until the eggs are set. Add salt and freshly ground pepper before serving.