And I am not talking about some out of the way cafe, or some far distant suburb. There is a great place for an excellent three course lunch in centre of the city. It is underground, but easy to find, though its advertising is minimal. No flashy signs - and no terrase either. Also only water to drink - just the stuff that comes out of the tap. And you are doing a Good Deed by eating here.
Restaurant Associatif, Foyer de la Madeleine offers a €15 prix fixe 3 course menu from 11:45am until 2pm Monday to Friday. Or you could join the Association for €5 and eat there more often for €8. I got the impression that most people there are regulars. The choice is limited - especially if you turn up close to 2pm as we did - but the cooking is excellent. All the service is provided by volunteers, and the price you pay helps provide subsidized meals for the needy and support other good causes - I think today it was for a hospital in Vietnam.
If your French is good or you can tolerate the English that Google turns it into they do have a web page
Today the menu was Soupe du Poisson, Cassoulet, Tarte aux Girolles, Tarte aux Poireaux, Endive Braisees, and Puree. We were offered a choice of cold entrees, I chose something that looked a bit like cold ratatouille with fish and my partner had an avocado with shrimps - and someone else at our table (we were asked to share) had a salad. As the Cassoulet was all gone we all three asked for the alternate Pork and Beans with the endive on the side, and each of us was given a delicious chocolate eclair for dessert. There may have been other choices too, but they did not even get considered.
We did not know of the restaurant's existence before: we were simply standing in the rain outside the church wondering where to get lunch when my companion noticed a sign near what I took to be the entrance to the crypt. This is half way along the eastern wall (Madeleine is oriented roughly north-south, oddly for a christian church). I thought it was probably a soup kitchen for the homeless - and indeed at the next table there were some people who could well have fitted that description.
I certainly did not miss professional wait staff - or the lack of a paper menu. And it may well be I have misrepresented the available choices, especially for those who like to eat lunch early. But I can heartily recommend good food where you get a square meal for the same price many restaurants charge for a burger!