Step 1Set aside 48 of the raspberries for garnish. Place the remaining raspberries, 3 tablespoons sugar, and the lemon juice in a saucepan over medium-low heat and cook until the fruit is very soft, 10 to 15 minutes. Remove the mixture from the heat and allow it to cool to room temperature.
Step 2Puree the raspberries in a blender, stirring as needed, then transfer to a bowl. Cover with plastic wrap and refrigerate at least 1 hour.
Step 3Heat the oven to 400 degrees. Generously coat the inside of the eight ramekins with butter. Then coat the butter lining with 2 tablespoons of the sugar.
Step 4Place the egg whites in the bowl of an electric mixer with the whisk attachment on low speed. Whip the whites until they form soft peaks, then gradually add the remaining sugar, continuing to whip until the egg whites form stiff, glossy peaks.
Step 5Remove the egg whites from the mixer and gradually fold in three-fourths cup of the raspberry puree, adding it in three batches and taking care not to over-mix. Reserve the remaining puree.
Step 6Using a pastry bag with the large plain tip, pipe the souffle mixture into the ramekins, swirling it so each souffle has a peak like a soft ice cream cone. (Alternatively, just spoon the mixture into the souffle dishes or ramekins, filling them not quite to the top.) Gently push 6 reserved raspberries into the top of each souffle.
Step 7Place the souffles on a baking sheet and put them in the oven immediately. Bake until puffed and golden, about 15 minutes. The center of the souffle should still be soft. Add a few tablespoons of water to the reserved raspberry puree to thin it out to sauce consistency. Dust with powdered sugar and serve immediately, garnished with the raspberry sauce.