[GIS] Contour of single feature on QGIS

Question

I'm trying to extract one single contour line at given elevation from a DEM. Taking into account that I want only one contour and not all contours with the given elevation, is there a way to do it in QGIS?
What I really want it is a tool similar to the contour drawing in ArcView. Just one click on DEM or GRID into the main view e the contour is drawn. I'd like to reproduce something like that.

Answer 1

You can use the SAGA Contour lines from grid tool, and there set both the minimum and maximum to your elevation contour of choice

Here's an example with an elevation of 500 meters