A good party calls for cake. And if you happened to have been celebrating Cosmonautics Day on the International Space Station, you ate your cake out of a tube.

On Thursday, the ISS crew marked cosmonaut Yuri Gagarin's landmark 1961 achievement as the first human in space by enjoying Moscow cake, a confection made with nuts and condensed milk that is served in squeeze tubes. The tubes are a throwback to the early days of space food.

Cosmonaut Oleg Artemyev tweeted a photo of the crew showing off their red tubes. The ISS currently hosts three NASA astronauts, two cosmonauts and an astronaut from JAXA, Japan's space agency.

JAXA's Norishige Kanai shared a close-up of his empty cake tube on Twitter. He described the dessert as sweet, and mentioned feeling a mix of excitement and trepidation about eating it.

The tube cakes reached a limited Earth-bound market in Russia in 2017, when the sweet souvenirs went on sale at the Moscow Planetarium, according to a report from Russian packaging news site Upakovano. 

Astronaut food has come a long way since the tube days. They now have everything from pudding to pizza parties to full-on Thanksgiving dinners.