Line a baking sheet with aluminum foil. Set a small baking rack on the baking sheet.
Meatloaf:
Add ground sirloin to a large mixing bowl, break up with a fork. Add the remaining meatloaf ingredients and mix well. Spoon and press into the prepared Bundt pan.
Place 2 cups of water in the Instant Pot liner, add trivet. Using an aluminum foil sling or long handled Instant Pot trivet lower the pan into the liner.
Set Instant Pot using [Manual] or [Pressure Cook], set time to 20 minutes. When pot beeps hit cancel and release the pressure. When the pressure has released remove lid and check the temperature with an instant read thermometer, it should read 155 degrees.
Remove meatloaf from the Instant Pot. Carefully drain the liquid from the meatloaf and then invert over a metal rack. Place rack with meatloaf on a baking sheet lined with foil.
Topping:
Set oven to broil.
Combine the topping ingredients in a 1 cup measuring cup, stir well until completely blended.
Spoon topping over the meatloaf, place under the broiler (6 inches from the heat) and broil until the topping just starts to bubble. Turn off oven and remove meatloaf. Gently slide onto a serving platter.
Traditional Oven Directions:
Prepare meatloaf as directed for instant Pot. Shape into 2 loaves on a baking sheet. Bake at 350 degrees for 40-50 minutes. Pour topping over loaves and bake an additional 5-6 minutes.