It’s tradition for couples to freeze the top tier of their wedding cake and tuck into a slice on their one-year anniversary.

David and Anne Cowburn have taken it a little further.

On every anniversary for the past 49 years, the West Grove, Pa., couple has enjoyed a slice of their wedding cake — or crumbs, in recent years.

The pastry, which they’ve kept in the freezer for a half-century, has survived five house moves. Every year on July 18, they thaw a small piece to share.

“It’s just a fun, romantic thing that we do,” Anne, 74, told The Post.

The Cowburns, who have three children and four grandchildren, delight in remembering their 1970 wedding, where they first cut into the three-tiered vanilla confection.

“It was a very special cake,” said Anne, remembering its white-frosting flowers and silver-leaf accents. “And there was so much of it.”

Luckily, neither has become sick after eating the cake. Or, as David, a 75-year-old retired educational administrator, put it, “It’s neither plentiful nor toxic.”

The duo met in 1967, when they worked as teachers at a junior high school in Wayne, Pa. They started dating a year later and married two years after that. Around 125 guests attended their ceremony and reception in Wilmington, Del.

Anne’s mom saved the top tier of the cake, which measured around 4-by-5 inches. She presented it to her daughter and new son-in-law after they returned from their honeymoon in England.

“Our first anniversary, we ate quite a lot,” said Anne, who went on to work at a bank.

They got the idea to preserve the cake from the old TV game show “I’ve Got A Secret,” hosted by Garry Moore. Panelists were tasked with guessing contestants’ secrets. One couple’s secret? “We’re going to eat the last piece of our wedding cake tonight. It’s 25 years old.”

“That episode must have embedded into my memory,” said David.

The couple plans to bake the last remaining crumbs into a new cake to celebrate their golden wedding anniversary next year.