Add the water to a large pot and bring it to a boil. For the orange, peel it using a potato peeler or a knife, then cut it in half. Cut the lemon in half and juice it. Add the remaining brine ingredients to the pot (excluding the ice) and bring to a boil to dissolve all the salt and sugar. Add the lemon halves and orange halves after they've been juiced to the brine as well as the orange peel, lemon juice and orange juice, they will provide more flavor. Remove from heat and cool completely. To speed this up add about 4 cups of ice to the brine. I used my instant pot for this but any big pot that will fit the brine and the breast will work.
Once the brine is cooled, place the turkey breast in the brine making sure it's fully submerged in it. You may have to weigh it down with another pot of water. What I did is wrapped the pot with plastic wrap, then placed a plate over it, and then a pot of water over the plate. This worked for me because the brine and turkey came up to the top of the pot. Another option is to use a brick or rock wrapped in plastic wrap. Store it in the fridge overnight or at least for 12 hours, so make sure you have enough room in your fridge.
Roasting the Turkey Breast
Preheat your oven to 350 F degrees. Remove the turkey breast from the brine solution and pat it dry with paper towels.
Place the quartered onions and smashed garlic in a large metal roasting pan then place the turkey breast on top of the onions. Season it generously with salt and pepper on both sides.
Brush the turkey with melted butter, keep remaining butter for basting later. Add the chicken broth to the pan.
Cover the pan with aluminum foil and place the roasting pan in the oven. Cook covered for 1 1/2 hours, basting with the melted butter (remelt again if necessary) every half hour. After 1 1/2 hours, remove the aluminum foil and roast for another 1 hour or until golden brown. The breast is done when a meat thermometer inserted in the thickest part of the breast registers at 165 degrees F.
Transfer the turkey breast to a platter or cutting board and let it rest for a full 15 minutes before slicing into it.
Skim some of the fat from the pan drippings if necessary.
Place the pan on the stove over medium-high heat. In a little bowl whisk together the cornstarch with the water, then add it to the pan. Whisk everything together. If the gravy is too thin and you prefer a thicker consistency, feel free to add more cornstarch until you reach the desired consistency. Cook for a few minutes, until the gravy thickens a bit. Taste for seasoning and adjust with salt and pepper as necessary.
Strain all the liquid into a bowl, then press all the liquid out of the onion and garlic using a spatula, for additional flavor.
Turkey breast cooking guidelines:
4 to 6 pounds - 2 1/2 to 3 hours
6 to 8 pounds - 2 1/2 to 3 1/2 hours
The best way to check to see if the turkey is cooked is to use a meat thermometer to make sure the internal temperature of the breast registers at 165 F degrees, in the thickest part of the breast. Sometimes a turkey/turkey breast will have a pop up timer (you can see in pic/video) which can be helpful as a preliminary step in judging the correct temperature.
Use a shallow metal roasting pan so that the oven air can flow completely around the turkey breast, which is also why I place the turkey on onions, to elevate it a bit.
Please keep in mind that nutritional information is a rough estimate and can vary greatly based on products used.