That seems to be how it's used in the article and some of the comments here:

"Crimea was the ideal site for this post-Soviet reunion, since it was the place where so many children, now adults, had spent their happy summer vacations, flocking there from all over the Soviet Union. For post-Soviet people, Crimea was a gigantic madeleine."

I see others have beat me to a response. m-w also has a paragraph about it:

"The madeleine is said to have been named after a 19th-century French cook named Madeleine Paumier, but it was the French author Marcel Proust who immortalized the pastry in his 1913 book Swann's Way, the first volume of his seven-part novel Remembrance of Things Past. In that work, a taste of tea-soaked cake evokes a surge of memory and nostalgia. As more and more readers chewed on the profound mnemonic power attributed to a mere morsel of cake, the word madeleine itself became a designation for anything that evokes a memory."

I had never heard of it either.