2 days in advance: Make rainbow topper. Tint 4 oz. fondant
royal blue. Roll out 1/8 in. thick. Cut an 8 in. circle using 8 in.
cake circle as a pattern. Center and attach Dora topper from
treat stand over circle using thinned fondant adhesive. Trim
fondant straight across bottom, even with topper, leaving a
1 1/2 in. fondant border around topper. Slit fondant to match
slits in topper. Tint fondant: sky blue, violet, rose, yellow
(1 oz. each); add 1/8 teaspoon Gum-Tex to each. Roll out 1/8
in. thick as needed. Cut and attach 1/2 in. wide rainbow strips
around topper (in order): 14 in. violet; 15 in. sky blue; 16 in.
yellow; 17 in. rose. Let dry. Reserve excess fondant.