Cut off pepper’s edges to get a kind of pepper cylinders and take stems and seeds off, remain edges for other dishes. Grease 12 1/2” 8 1/2” baking tin with 1 Tbsp of EVOO, settle pepper cylinders vertically and bake them for 5-7 minutes, pull out and let them cool down.
Preheat medium skillet to a medium low. Dice onion finely and sweat with remaining olive oil for 5-10 minutes, add garlic and butter, sweat another 3-5 minutes and set aside to cool.
In a bowl combine ground beef with flax and psyllium, add sweated vegetables, do not skip the fat from sweating. Season filling with 2 Tsp of salt and spices to taste. Mix well, form balls with wet hands and stuff cooled pepper cylinders from the top.
In a sauté boil the water and season with remaining 1 Tsp of salt and any other spices you love, add diced tomatoes, stir and pure the mixture all over the tin with stuffed peppers
Bake for 35-40 minutes and serve with full-fat plain yogurt, garnish with basil.