OED on “take the cake”:
7. a. Cake is often used figuratively in obvious allusion to its estimation (esp. by children) as a ‘good thing’, the dainty, delicacy, or ‘sweets’ of a repast. So cakes and ale, cake and cheese (Scotl.). to take the cake, (U.S. cakes): to carry off the honours, rank first; often used ironically or as an expression of surprise. Cf. BISCUIT 1d.
1579 [see 2]. 1601 SHAKES. Twel. N. II. iii. 124 Dost thou thinke because thou art vertuous, there shall be no more Cakes and Ale? 1606 DAY Ile of Gulls III. i. (1881) 68 That’s Cake and Cheese to the Countrie. 1847 W. T. PORTER Quarter Race Kentucky 120 They got up a horse and fifty dollars in money a side,..each one to start and ride his own horse,..the winning horse take the cakes. 1854 Blackw. Mag. LXXVI. 702 Malcolm is, par excellence, the ‘cake’ of the corps dramatique. 1884 Lisbon (Dakota) Star 25 July, Sherriff Moore takes the cake for the first wheat-harvesting in Ransom county. 1886 Garden 5 June 519/1 The gardener’s life, as a rule, is not all ‘cakes and ale’. 1886 Pall Mall G. 2 Sept. 5/1 As a purveyor of light literature..Mr. Norris takes the cake. 1900 T. DREISER Sister Carrie xxiii. 249 Pack up and pull out, eh? You take the cake. 1904 A. BENNETT Great Man xxv. 275 My bold buccaneer, you take the cake… There is something about you that is colossal, immense, and magnificent. 1938 G. HEYER Blunt Instr. ix. 158 I’ve met some kill-joys in my time, but you fairly take the cake.
So it seems as if “cakewalk” is related to “take the biscuit”
d. Colloq. phr. to take the biscuit: to ‘take the cake’ (see CAKE n. 7).
1907 G. B. SHAW John Bull’s other Island III. 76 All you know is ah to ahl [howl] abaht it. You take the biscuit at that, you do
and derives from the sense of “cake” referred to in “cakes and ale” and “take the cake” dated from the first citation from horseracing of 1847, though there’s no specific evidence in OED, as you say.