Slice the eggplant in half lengthwise and hollow out the halves leaving about a 1 centimetre shell. Set the flesh from the insides aside for later use. Place the shells on a baking tray, and drizzle with a little olive oil.
Bake for about 30 minutes in the preheated oven, until soft.
While those are baking, chop the leftover eggplant into small pieces. Heat about 2 tablespoons of olive oil in a large frypan over medium heat. Add the onion and garlic; cook and stir for a few minutes. Add the chopped eggplant; cook and stir until tender. Mix in the tomatoes and tomato paste until well blended. Simmer over low heat until the halves in the oven are ready.
Remove the baked eggplant shells from the oven, and spoon in the tomato and eggplant mixture. Sprinkle a little cinnamon over the top of each one, and return them to the oven. Bake for another 20 minutes or so.