Rokeg blood pie was a traditional Klingon food.
William T. Riker claimed to enjoy Rokeg blood pie while aboard the IKS Pagh in 2365. (TNG: "A Matter Of Honor")
Rokeg blood pie was one of Worf's favorite foods; when he was a child, his adoptive mother Helena Rozhenko learned how to prepare it just for him. However neither she or her husband ever learned how to eat it. Worf ordered the dish on the Rotarran in 2374. Helena Rozhenko mentioned this when she and her husband Sergey Rozhenko were surprised when Guinan informed them of Worf's affinity for prune juice. (TNG: "Family"; DS9: "Sons and Daughters")
It was traditional to eat Rokeg blood pie on the Day of Honor. (VOY: "Day of Honor")
It was not specified, but is likely that this pie is prepared with real blood.
According to the Star Trek Cookbook, the pie was pumpkin pie mix colored with fruit juice. Beets were used to create the "hairy" appearance.