This dessert fully satisfying, yet low in fat.
Grate zest and squeeze juice from lemon; set both aside. Cut plums in half and discard pits. Quarter each half lengthwise and place in a round 12-by-2-inch casserole or saute pan. Sprinkle plums with 4 tablespoons sugar and drizzle with lemon juice, kirsch, and 3 tablespoons water.
Place over high heat and bring to a boil. Reduce heat to medium low and simmer until the plums begin to break down, about 15 minutes, depending on ripeness.
Meanwhile, sift together the flour, remaining 3 tablespoons sugar, baking powder, baking soda, and salt. Whisk in lemon and lime zests. Stir in the cream and buttermilk until just combined.
Drop batter by heaping tablespoonsful over plums; there should be enough to make eight dumplings. Cover casserole (if casserole does not have a cover, use foil), reduce heat to low, and simmer until the dumplings are doubled in size and cooked through, about 20 minutes. Remove from heat, uncover, and let cool on a wire rack for about 15 minutes. Serve warm.
When you lift the cover off the casserole in step four, be careful not to let the condensation run off into the dumplings.