Recursion Visualizer is an app that lets you code a recursive function and then visualize the recursion tree, along with the order in which the recursive functions are called. The visualizer works with any recursive function, as long as the code does not enter an infinite loop and the recursion does not go down too many levels. Some good functions to try out are Fibonacci, Binomial Coefficient, and Quicksort (templates are included). The visualizer also works with recursive functions using memoization, so you can see how an algorithm's time complexity improves when storing the results of previously computed functions.
Check it out here: https://recursion-visualizer.vercel.app
FYI If the code is not executing, that means I'm no longer hosting the backend server, sorry