I took on the monumental personal task of identification and cataloging of every seed/nut that I find in my area. I live in Eastlake, Ohio, a suburb of Cleveland and travel the local Metro Park systems regularly. I use field guides to assist in the samples I find. But I found something that stumped me. The subject in question, was found alone with no other samples around for at least a 10 foot perimeter. In good light, it appears to be red with pale yellow or possible off white specks. Outer coating is slightly bumpy and a fingernail can penetrate if pressed hard enough. It is spherical with a tapered top, most likely the point of separation from the stem. It is slightly larger than a quarter. Since this is my first time here, I am uncertain as to whether or not the photos uploaded. Will post and see.
What does the inside of this dare-I-say fruit look like...? Outlandish guess: some kind of wild fig. Welcome to the Forum! (I have a good friend who spent his formative years in Eastlake.)
Take a look inside. The fleshy interior does resemble a fruit. I would have agreed with the fig statement if it weren't for the unusual, mottled skin. In my experience, figs tend to flow from one solid color to another during their maturation process. By the way, I found it in a forest of maple, oak and poplar, if that helps.
I dug around a bit more and made a remarkable discovery. What I found here is an Acorn Plum Gall. The white thing in the center is the larva of Amphibolips quercusjuglans, otherwise known as the Gall Wasp. Injected into the center of an immature acorn, it would eventually develop into a wasp. Perfect shelter and food source.