Preheat the oven to 375F.
Grind the meat together with the onions on a medium size plate. Add the cooked rice, the salt and the chopped coriander and dill. Mix well and set aside.
Slice off the bottom (or top, whichever you prefer) side of the tomatoes with a sharp knife, cutting about 1/4 - 3/8-inch from the edge. Carefully scoop out the flesh with a teaspoon, making sure you do not rip the outer shell. Put the tomato flesh in a separate bowl, mash with your hands and set aside until needed. Place the tomato shells in the baking dish, spacing them out evenly. Sprinkle a little salt and pepper inside the shells. Stuff them with the meat and rice stuffing, replace the tops, and place the tomatoes into a deep baking dish. Roast at 375F for 60 minutes or until the internal temperature of the stuffing reaches 165F. I like using my BBQ thermometer with an alarm. This way I don't have to worry about my stuffed tomatoes and they always come out perfectly cooked.
Meanwhile, prepare the sauce. Heat the butter in a skillet over medium-high heat. Once the butter starts to get dark, add the chopped onions and saute until golden brown, about 5-7 minutes. After that add the flour and keep sauteing, frequently stirring, until the flour is well incorporated, about 1 minute. Add the mashed tomato flesh with all the juice and saute for another 5-7 minutes, until the sauce has thickend. Finally, add the sour cream and saute, frequently stirring, until well incorporated, about 1 minute.
Remove the tomatoes from the oven. Take off the tops, pour a couple ot tablespoons of hot souce over each tomato, put the tops back on and serve immediately.