Preheat oven to 325°F.
Line a large roasting pan with foil.
Making 1/2-inch-deep slits, score ham with a diamond pattern.
Place ham in the pan and add 1/2 cup of water.
Cover the ham with pineapple rings, securing each ring with a toothpick.
Cover with foil and roast for 45-60 minutes to heat thoroughly.
Combine brown sugar, Pineapple Balsamic Vinegar, and mustard in a small saucepan.
Bring to a low simmer, stirring until the sugar melts.
Add butter and whisk until smooth and uniform.
Season with salt and pepper to taste.
Remove from heat, but keep warm.
Uncover ham and baste ham with glaze.
Continue to roast ham and pineapple until deep brown and glazed, brushing ham with glaze every 10 minutes for an additional 30 minutes.
Transfer ham to large platter.
Remove Pineapple rings and serve with ham.
