When you cast a card with fuse for both halves is it one spell or two? {turn/burn} {guttersnipe} {Cancel}. Does guttersnipe deal 4 damage for turn and burn? Can you cancel one fused card with cancel?
It's one spell, called a fused split spell:
702.101a (http://imtgapp.com/forum/index.php?action=imtg;area=rule;number=702.101a): Fuse is a static ability found on some split cards (see rule 708, "Split Cards") that applies while the card with fuse is in a player's hand. If a player casts a split card with fuse from his or her hand, the player may choose to cast both halves of that split card. This choice is made before putting the split card with fuse onto the stack. The resulting spell is a fused split spell.