Rinse orange, cut in half lengthwise, then slice crosswise; discard seeds.
In a 10- to 12-inch nonstick frying pan, combine orange, 1/4 cup sugar and 2 tablespoons water. Stir often over medium-high heat until liquid evaporates, 4 to 5 minutes; take care not to scorch fruit.
Cut pears lengthwise into 3/4-inch slices and mix with lemon juice. In a 10-inch-wide (about 8-cup) round quiche dish or shallow casserole, snugly arrange pears in a single layer. Tuck orange pieces among pear slices. Spoon brandy over fruit, then sprinkle evenly with remaining 2 tablespoons sugar.
Bake in a 450° oven until fruit edges are tinged with dark brown, 25 to 30 minutes.
Stir apricot jam to soften; dot evenly over fruit.
Return dish to oven and bake until jam is bubbling, about 5 minutes. Spoon portions onto plates.