Peel cucumbers and slice in half lengthwise. Scoop out all the seeds with a spoon. Slice in half-moons, about 1/4 to 1/3-inch thick. Heat butter in large heavy skillet over medium flame. Be careful not to let the butter brown, but it does need to be good and hot. Add the cucumbers and shallots and cook, tossing often, until the cucumbers begin to get tender, about 4 minutes. Stir in dill, plus salt and pepper to taste. Continue to toss and cook until crisp-tender, 1 to 2 minutes longer. Serve immediately.