WaterProofing (and WeatherProofing) gaps in roof
The best way to remedy this is to remove the portion of metal over the transition to cement roof, add a transition flashing that goes over the cement roof. It should cover at least the first row of exposed cement tile at the top and the metal is folded so it turns up the higher pitch, but goes under the metal roof at least as high as a few inches above the first row of fasteners at the bottom of the metal. Do not fasten the metal flashing through to the cement tile. The metal needs to be bent so it presses in place onto the cement tile. You may be able to remove just enough metal fasteners, if they are exposed to ease up the metal roof enough to slip the transition flashing under it without removing all of the metal. Your biggest issue will be working off the cement roof without cracking the tiles. A picture of the trouble spot may help fashion a better answer.