Press Saute and set it for Medium, Normal or Custom 300°F and set time for 20 minutes. If needed press Start.
As the pot heats, melt the butter in the insert set in a 5-, 6-, or 8-quart Instant Pot. Add the onions, sugar, and 1/2 teaspoon salt. Cook, stirring quite often, until the onions soften and even brown, about 15 minutes.
Meanwhile, mix the ground beef, egg, bread crumbs, seasoning blend, pepper, and remaining 1/2 teaspoon salt in a large bowl until uniform. The egg should be thoroughly blended in the mixture.
Divide the ground beef mixture in half. Form each into a flat, 7 inch long oval. Put the cheese down the middle of one of the ovals. Top with the other oval and press the edges to seal well. Compact the mixture gently into a meat loaf without breaking through to the cheese.
When the onions are ready, add the brandy and Worcestershire sauce to the pot; scrape up any browned bits on the insert’s bottom. Stir in the broth and turn off the heat.
Set a pressure- and food-safe rack or trivet in the pot over the onions. Set the meat loaf on the rack. Sprinkle the meat loaf with the paprika and lock the lid onto the cooker.
For the Max model: Set the pot for Pressure Cook and set the Level to Max. Set the time for 20 minutes with the Keep Warm setting off. For all other models: Set the pot for Pressure Cook or Manual. High Pressure and set time for 25 minutes with the Keep Warm setting off. Slow Cooker Function: Set the pot for Slow Cook and set the level to High. The valve must be open. Set the time for 3 1/2 hours with the Keep Warm setting off.
When the pot has finished cooking, turn it off and let the pressure return to normal naturally, about 35 minutes. Whichever cooking method you used, unlatch the lid and open the cooker. Remove the meat loaf from the pot by using silicone baking mitts to pick up the (hot!) rack it’s sitting on. Transfer to a nearby cutting board. Whisk the water and cornstarch in a small bowl until smooth.
Press Saute. Set it for Medium, Normal or Custom 300°F. Set time for 5 minutes. If needed press Start.
As the onion mixture comes to a simmer, whisk in the cornstarch slurry. Continue cooking, whisking constantly, until somewhat thickened, less than 1 minute. Turn off the heat and use hot pads or silicone baking mitts to transfer the (hot!) insert from the pot to a nearby wire rack. Cut the meat loaf into 1-inch-thick slices and serve in bowls with the onion sauce ladled over the top