What does one serve to royalty? This Hyde Park-baked coffee cake.

“There was some tea and My Grandma’s in the room,” when she welcomed Prince William and Kate to City Hall last month, Wu said, offering two of the same cakes up to the GBH hosts.

Wu also described the gifts her family had bestowed upon William and Kate: a copy of the famous children’s book “Make Way for Ducklings,” along with a letter from her two young sons to the royal couple’s three children; a live-edged wooden bowl made from a tree in the Arboretum; and a regional favorite, a fish-shaped jug known as a “gurgling cod.” Wu hosted the royals at City Hall on Nov. 30 for the first appearance in their three-day visit to Boston, which included a Celtics game and a walk along the harbor and culminated in a star-studded awards ceremony for climate innovation.

Just a few days earlier, when he learned that the royals were visiting Boston — via a story in the Boston Globe — My Grandma’s President and Owner, Bob Katz, called City Hall to offer up his bestsellers.

“It’s such a historic thing,” he said. “I wanted to be part of it in any way. What more proud way to invite someone to Boston than with our coffee cakes?”

The bakery donated three cakes for the city to serve William and Kate at tea time: cinnamon walnut, their most popular; granny smith apple; and the “Red, White, and Blue Patriot” cake, which features cranberries and blueberries. For the royals to take home, Katz sent one “Ted Williams Chocolate” and one pineapple coconut cake, selections he expected to be popular with the couple’s children.

Founded in 1990 in Newton, using the legendary coffee cake recipe of founder Barry Cohen’s grandmother, My Grandma’s of New England is now a mostly mail-order bakery based in Hyde Park. Katz, who bought the business in 1993 and moved it to Boston in 1997, estimated that it will sell more than one million cakes this year.

This was hardly the first brush with fame for the bakery, which Katz said used to donate cakes to former Mayor Thomas M. Menino to give out to constituents. The cakes have also gotten shout-outs on shows including the “Sopranos” and Al Roker’s ”Roker on the Road.”

But “this is the apex,” Katz said.

“Giving cakes to royalty is one of the highest honors,” he said. “Twenty years from now, this will still be in the top two or three” moments for the bakery, he said.

And it may not be over yet, he added.

“If the prince calls and wants more cake,” Katz said, “I would not be surprised.”

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Emma Platoff can be reached at [email protected]. Follow her on Twitter @emmaplatoff.