C++11 is probably as close as you can get to something that's simple enough and widely used but also supports diving into how computers work because you will eventually have to manage your own memory (although I'm not sure if memory management is an important skill for someone just starting to learn how to code).

For a real deep understanding, you'd probably have to jump into the actual computer microchip architecture to learn how computers store memory and do things like pipelining, branch prediction, and caching. Then a primer on Operating Systems (I like "Three Easy Pieces") should fill in the gaps.

I would choose Asm or perhaps even raw machine code.