It's a genuine Heinz-approved recipe from Kraft Canada, which makes baking products.
The social media frenzy last week prompted one man, Gregory Nuttle, the University of Nevada's director of graduate student services, to try out the recipe.
He filmed it step-by-step in three videos on YouTube.
His verdict? Surprisingly 'not bad' - apparently it tastes similar to a spiced carrot cake.
His friends, who were brave enough to try his creation, described it as "perfectly acceptable", "moist", and "sweet".
One friend said: "It is very similar to a carrot cake, with a finer crumb."
Gregory, a vegan, even tried the recipe - containing eggs and cheese - himself, explaining: "I spent a lot of time on this, I'm doing it."
His friend joked: "Does it taste like pain and animal suffering?"
Sounding surprised, Gregory exclaimed: "It's pretty good!"
But Gregory wasn't the first one to test the recipe at the request of Reddit.
A year ago, before the picture went viral, @Showmm created a step-by-step guide of how to make the ketchup cake, with pictures at every stage.
Her cake was not the luminous red depicted on Kraft's website, as she had run out of red food colouring, she told picture-sharing website Imgur.
She said the taste was "fine" - a ringing endorsement.
She wrote: "Maybe there was a very slight hint of tang to the cake, but you wouldn't know it was ketchup. It tastes like spice cake!"
The recipe was created for the 100th anniversary of Heinz in Canada, according to Kraft.
Describing the cake, it wrote: 'This showstopping cake tastes as good as it looks.
"If you are a fan of carrot cake, you'll want to try this recipe!"