Heat the oven to 425°F and arrange a rack in the middle.Stir all of the ingredients together in a 9-inch pie plate and spread the cherries into a single layer. Roast, stirring occasionally, until the cherries are softened, juicy, and bubbling, about 20 minutes.
Place the matzo pieces in a 13-by-9-inch baking dish and spread them into an even layer.
Add the water and gently stir until the pieces are evenly moistened.
Let sit until the water has been absorbed, about 1 to 2 minutes.
Whisk the eggs and salt in a medium bowl until the eggs are broken up.
Pour the egg mixture over the softened matzo and stir to combine.Melt the butter in a large nonstick frying pan over medium heat until foaming.
Add the matzo mixture and, using a rubber spatula, press it into an even layer. Cook undisturbed until the bottom is golden brown and the mixture is set, about 5 to 7 minutes.To flip, slide the brei onto a large plate.
Place a second large plate upside down over the brei and invert it onto the second plate. Slide the brei back into the pan and reshape it if necessary with the rubber spatula. Cook until the second side is golden brown, about 7 to 8 minutes more.Slide the matzo brei onto a cutting board and slice it into wedges.
Transfer the roasted cherries and their juices to a serving bowl.
Serve the matzo brei warm, passing the roasted cherries, and cinnamon and sugar (if using), on the side.
