Preheat the oven to 200C/440F/Gas 6. Cut the eggplant in half, leaving the tops on and score the surface of the flesh with a knife.
Place on a baking tray cut-side up, drizzle with olive oil and season with salt and pepper. Bake for about 30 minutes or until soft.
While the eggplant are cooking, gently fry the tomatoes and herbs and cook to soften
Remove the flesh from the roasted eggplant, reserving the skins to be stuffed later. Chop the eggplant flesh into small cubes.
Add the eggplant flesh and the lightly chopped walnuts to the tomato mixture and season generously with salt and pepper. Place the mixture in the eggplant skins (if making in advance, you can refrigerate the eggplant at this stage).
Crumble over the cheese and top with gluten free breadcrumbs. Return to the oven or place under a hot grill until the cheese is melted, the gluten free breadcrumbs crisp and the flesh warmed through.
For the tomato sauce, heat the oil in a pan and add the tomatoes and bring to the boil, add the chopped oregano reduce the heat and simmer for 30-40 minutes. Halfway through, add the shredded basil leaves.
When it has finished cooking, add salt to taste, and blend to a smooth purée using a hand-held blender or food processor.
The sauce keeps for a few days in the fridge, but is best if eaten when freshly made. Serve the hot eggplant with the hot tomato sauce on the side.