When chomping into the Macau pork-chop bun at Pearl River Deli, the first sensation that rolls over your taste buds is obvious: meat. Breaded, fried, appealingly nubbly meat. It takes about eight seconds before more intricate flavors start to sing out in harmony.Tomato-onion relish, simmered to jam with garlic and capers, introduces sour, sweetness and tang. You might first notice the sugar sprinkled atop the bolo bao — also known as a pineapple bun for its turmeric-yellow color and patterned crown, not for any presence of fruit — as a texture that grazes the roof of your mouth.