Tiffani Thiessen was born January 23, but it'd be hard to tell from her recent video post, where she eats a cake ... apparently wearing nothing but her birthday suit!

The "Saved by the Bell" alum totally teased fans with her recent Instagram post ... appearing topless while enjoying her sweet treat ... and asking fans, "How do you eat it?" Getty

Her caption -- "When it’s hot out, you gotta get naked…" -- made it clear she was commenting on the naked carrot cake instead of her naughty body -- so relax, Mr. Belding! Getty

TT even dropped her recipe for the dessert -- called "naked" 'cause unlike traditional cakes, the carrot version has little to no frosting on the outside. Remember, she once hosted the Cooking Channel show "Dinner at Tiffani's" ... so, the girl knows her st

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