Core the peppers by using a sharp pointed knife to cut about a centimeter around the stem, removing the stem, as well as all the seeds and white fibers from the inside of the peppers.
To make lids for the peppers, slice the skin off the tomatoes, cutting out round disks that are around the same size as the openings in the peppers.
Set the tomato lids aside, and blend the rest of the tomatoes in a food processor or blender with a cup (250 ml) of water until they are fully blended and set it aside.
prepare the filling
Heat 2 tablespoons of vegetable oil over medium-high heat in a non-stick skillet.
Sauté the onion until slightly reduced and beginning to brown (3 minutes)
Add the tomato paste, rice. and remaining tablespoon of oil. Sauté another 2-3 minutes until the mixture is very dry and starting to sizzle.
Add a cup of water (250 ml), a quarter cup at a time allowing the mixture to reduce, dry out and sizzle in between. This will caramelize it and bring out more flavor.
After all the water is added, turn off heat and add another half cup of water. Mix and set it aside to cool for a few minutes.
assemble and cook
Combine the ground meat with the cooked rice onion mix and all the seasonings (except the bay leaves). Mix until homogenous.
Put the peppers into your pot. They should be snug enough that they hold one another up. See recipe post for details.
Use a spoon to fill the peppers with the filling. You can press the filling down a bit to fit more, but don't overfill or the peppers can break open when the rice expands. See recipe post for details.
Gently press the tomato lids into the opening of the peppers, so they sit in the pepper under the lip of the opening.
Once all the peppers are filled and covered with lids, pour the blended tomato over them and place the bay leaves between the peppers, pressing them down so they're touching the liquid.
Cover and bake in a preheated oven for one hour.*
Notes
* It's also very common to cook stuffed peppers on the stovetop. Personally I like the flavor that develops from the drier heat of the oven (and the fact that it feels more hands-off to just put the pot in, set-it-and-forget-it style) but if you don't have an oven or prefer the stovetop you can use that instead. Cook on the stovetop over medium-low heat for 50-60 minutes.