PREHEAT OVEN TO 350°. GREASE AND FLOUR A 10" BUNDT OR TUBE PAN. SET ASIDE.
COMBINE CAKE MIX, EGGS, OIL, 3/4 CUPS WATER AND 1/4 CUP KEY LIME JUICE IN A LARGE MIXING BOWL. BEAT AT LOW SPEED WITH MIXER UNTIL MOISTENED. BEAT ON MEDIUM SPEED 2 MINUTES LONGER. POUR INTO PREPARED PAN AND BAKE FOR 50 TO 60 MINUTES OR UNTIL TESTER INSERTED IN CENTER COMES OUT CLEAN. REMOVE FROM OVEN AND COOL IN PAN FOR 15 MINUTES. REMOVE CAKE FROM PAN ONTO A WIRE RACK AND COOL UNTIL JUST WARM.
RETURN CAKE TO PAN AND POKE HOLES IN TOP OF WARM CAKE WITH TOOTHPICK, CAKE TESTER OR WITH A STRAW. POUR GLAZE SLOWLY OVER TOP OF WARM CAKE. COOL COMPLETELY.
INVERT ONTO SERVING PLATE. DUST WITH CONFECTIONERS' SUGAR AND GARNISH WITH LIME SLICES AND STRAWBERRY SLICES IF DESIRED.
GLAZE: COMBINE THE CONFECTIONERS' SUGAR, KEY LIME JUICE, WATER AND MELTED BUTTER IN A MEDIUM BOWL, MIXING UNTIL SMOOTH.