Preheat the oven to 400°. In a blender, combine the milk, flour, sugar, eggs, vanilla and salt. Blend until the batter is smooth, about 30 seconds.
In a medium ovenproof skillet, melt the butter over moderately high heat. Stir in the brown sugar, lemon juice and bourbon and cook until the caramel sauce is bubbling and beginning to darken, about 3 minutes. Add the pears and cook just until they begin to soften, stirring to coat them with the caramel sauce, about 3 minutes. Remove from the heat.
Arrange the pears in the caramel sauce in an even layer. Gently pour the batter over the pears and caramel sauce. Bake the clafoutis for about 30 minutes, until the top is puffed and browned. Dust with confectioners' sugar and serve hot or warm.