In a large bowl, mix the ground meats by hand, then add in the bacon, onion, garlic, eggs (make sure they are beaten before adding) and milk. Follow with the Worcestershire sauce, spices, bread crumbs and cheese. Combine all these ingredients using your hands, try not to overmix.
Turn meat mixture out onto a foil covered board and form into a round loaf that is about 4 inches thick. Use steamer ring to measure that it will fit into Instapot.
Add stock, diced tomatoes, seasoning and tomato paste to the Instapot. Stir until paste is incorporated into the stock.
Fold an 8 to 10 inch wide strip of aluminum foil into a strip about 3 inches wide. Place formed loaf on this strip, which will allow you to place and remove the loaf from the Instapot. Place steamer ring into pot (it may be covered by the sauce) and then carefully lower loaf onto the ring with the foil strip.
Lock the lid and cook at high pressure for 16 minutes. Allow the pressure to release naturally for about 10 minutes.
Preheat oven to 450 and line a rimmed baking sheet or appropiate sized oven proof dish with aluminum foil.
Carefully open pressure release lever. Once released, open pot and check to see that the internal temperature of the meat is 160 degrees (if not, you can re-seal lid, return to pressure and cook a few more minutes). Remove the meatloaf from the pot and transfer to a lined baking dish. Cover while you reduce stock.
On the Instapot, press sauté and adjust level to medium which should bring the sauce to a simmer. Simmer sauce, stirring often to avoid burning and reduce by about a 1/3 or until it is at a desired consistency, about 8 minutes.
Transfer thickened sauce to bowl and with silicon brush spread sauce over the meatloaf. Reserve extra sauce for serving.
Bake uncovered in oven for 10 minutes, slice and serve.