Heat a small skillet over medium heat. Toast almonds in hot skillet until fragrant and lightly browned, about 3 minutes.
Put almonds and brown sugar into a food processor bowl and process until almonds are chopped; add butter and pulse the mixture until completely blended.
Arrange peaches with the cut sides facing up into the baking dish. Spoon 1 tablespoon almond mixture into the center of each peach. Pour liqueur and water into the baking dish; cover with aluminum foil.
Bake in preheated oven until the peaches are tender, 20 to 30 minutes.