This is a hardcore Paleo recipe (Loren Cordain's style of the Paleo diet). No salt, no sugar, no processed foods (i.e., nothing canned), no dairy, no grains, no yeast, no starchy vegetables. Yet delicious!
Cut tops off green peppers. Remove seeds and membranes. Slice pepper in half from top to bottom (or leave whole if you prefer).
Remove edible portion of tops you just cut off and chop. Set aside.
Bring a large pot of filtered water to a boil and add green peppers. Boil, uncovered, for 5 minutes. Remove, drain well and arrange cut side up in a baking dish large enough to accommodate the peppers.
Preheat oven to 350°F.
Cook onions, peppers, tomatoes and garlic in hot oil in a large skillet until softened. Add ground beef and break up with wooden spoon. Sprinkle with Italian herbs, fennel seeds, crushed red peppers and black pepper. Mix well and continue to cook until meat is browned. Remove from heat.
Spoon meat mixture equally into bell peppers. Bake, covered, for 30 minutes.