Drop the kohlrabies into a large pot of boiling salted water and cook at a gentle bubble until tender when pierced. Drain in a colander. When cool enough to handle peel the kohlrabies and slice into ¼-inch-thick rounds.
Preheat the oven to 375°F. Generously butter a shallow baking dish. In a small saucepan, combine the cream, cream cheese, lemon juice, dill, salt, and pepper. Heat gently until the cream cheese melts. Whisk to blend and smooth out.
Arrange the kohlrabi slices in the prepared baking dish in overlapping rows. Pour on the sauce. Sprinkle the surface with paprika and then scatter the grated Gruyère cheese over the top. Bake for 20 minutes or until the surface is nicely browned.