The light tells us that whatever goes in there must be something that benefits from being lit from top-down. Given it’s height, it wouldn’t be a ‘work area’. Therefore we can conclude that it’s something for display or quick access.
These all point towards ‘hidden gun rack’. It’s possible that a prefabricated secret compartment was purchased and then installed on it’s side.

Alternately, a spice rack was simply used for an alternative purpose

Best guess: Spice Rack space saver, possibly repurposed for weapon display/access, or to display some esoteric hobby item like tea, stamps, etc.
EDIT: 3rd option – Someone wanted a hidden spice rack even though they didn’t have a good place for it. They tried to compensate for the poor location with a very nice flush/hidden finish. The holes were from the mounted racks.

That’s unique for sure. This pullout pegboard cabinet uses a narrow space but probably not how yours was used.
The sliding cover seems useless and the light and storage space is on the wrong side for easy kitchen access. Because of that I don’t think that was meant for kitchen stuff or cooking. Whoever guessed a hiding spot for something like guns might be right.
I have seen a similar sliding thing in a home that was used for homeschooling the kids. It wasn’t exactly like this, but it was a semi-permanent fold out board that could be seen in multiple rooms to hang stuff on. It’s a long shot, but it’s an idea. Not sure why it would go so in-depth if it was this.
Possibly storage for a large cookie sheet or cutting board or maybe pizza stone?Here’s an idea, shine a flashlight into the compartment where it slides back into and see if there are any clues there; old label, spilled spices, etc.
EDIT: The more I look at it, I’m thinking it is a purpose built sun shade. Someone may have then repurposed it as some type of storage, hence the light.

Take a look at where the television might have been in the adjacent room. Is there a time of day when the sun shines brightly in the kitchen window, through the doorway and onto a wall where a television may have once sat?

maybe to hang garden herbs to dry? I am also intrigued by this.
I’m not gonna lie I would put a copy of the declaration of independence up there
Pasta drying board?
The hole in the vertical piece on the back seems to imply that the wires could/would go all the way across the back. I wonder if those wires are 120v (assuming the light and undercabinet lights are 12v).Is the power for this thing on the same circuit as the kitchen? Or on a separate circuit (perhaps labeled “stolen art lighting”) in the fuse box.
A fun mystery to find in your house though.

it’s in the kitchen, going to guess for hanging larger kitchen/cooking utensils but no screws or hooks had been installed yet. Also the idea that it was for firearms is interesting too
I’m am so interested. He purposely build this in designing the kitchen. That is hardcore. I have a theory. I have to go with the concealing a painting. The light is there to show off his secret painting. Do you see any holes or hooks for the painting. Did the owner tell you about it? I bet not.
Probably to hide a leaf of a table
Obviously built with some skill and care by the cabinet maker, and then converted into something else in a half assed manner later when the light was added. My guess is it was originally used to store something that came with the cabinets, like extra shelves or a specially made cutting board or something. Reminds me of when table makers add a clever way to store the extra leaves.
Baking sheet storage.
I am in the process of buying a house in really hoping it has some cool surprises like this. I would go for hanging notes and things like someone else said though.
The room behind the first photo looks like a living room. Was the place occupied by the same people for a long time before? Maybe the TV was over there and the pull-out was for glare from the kitchen windows? I’ve seen crazier in houses.
Kitchen designer for 20 years: no idea.
What do you think? Let us know in the comment!