This one brings good memories, as my mom used to cook it for us; I just adjusted the recipe to my taste.
I cut off the top of 4 big tomatoes, so it looked like small hats and I cleaned the inside with a tea spoon. Then, I used the same technique for the tomatoes themselves and removed all the flesh. And as tomatoes are so beautifully juicy, my tip is to salt powder them and leave them to rest on a dish face down so all the excess of water would drain out.
On a bowl, I mixed about 500 grams of very fresh mince of beef with salt, pepper, thyme, fresh parsley, a small diced shallot, about a fourth of the tomato flesh finely diced and a egg yolk. And as always, I don't only put my heart in my cooking, but my hands as well ;) It's like my me-touch!
Finally, I filled the tomatoes up with the meat, still using my fingers, it's easier to make sure all the tiny spots are repleted.
I then layer two or three table spoons of a nice virgin olive oil on a terracotta oven dish and display there my tomatoes topped with their small hats and add there 4 medium size potatoes cut wedgies style with a bit of salt and again dropped some more olive oil. The whole thing then goes on the oven for 30 to 40 minutes, at wish. I personally prefer to have it very juicy.
I reckon we could also add small dices of mozzarella or fine stripes of bell pepper, or even replace the beef with finely diced veggies like mushrooms and eggplant.
Have it your way and enjoy!