The cell organelle that is the site of cellular respiration and produces ATP is the mitochondrion.

Here's why:

* Cellular Respiration: This is the process where glucose is broken down to release energy in the form of ATP (adenosine triphosphate).

* Mitochondria: These organelles are often called the "powerhouses of the cell" because they are responsible for producing most of the cell's ATP. They have a double membrane structure that allows for the separation of different stages of cellular respiration.

Let me know if you'd like more details on cellular respiration or the structure of mitochondria!