Preheat the oven to 400 degrees F. Butter a 10 by 2-inch round (1-quart capacity) baking dish. In the dish, toss the pears gently with the lemon juice and spread them out evenly.
In a blender finely grind 1/2 cup of the almonds, add the milk, 6 tablespoons of the butter, the eggs, the vanilla, and the almond extract, and blend the mixture until it is smooth.
In a bowl whisk together the flour, 1/2 cup of the sugar, and a pinch of salt and stir in the milk mixture, stirring until the batter is combined well. Pour the batter over the pears, drizzle it with the remaining 2 tablespoons butter, and sprinkle it with the remaining 2 tablespoons sugar and remaining 1/4 cup almonds. Bake the clafouti in the middle of the oven for 40 minutes, or until golden brown. Let it cool on a rack for 15 minutes. Serve the clafouti warm.