Preheat the oven to 160° C w/ fan.
Line the loaf tin crosswise w/ baking parchment.
Chop the onion after peeling & trimming.
Chop the bacon slices & add to the onion.
Start frying the mess in some butter - softly; take care that it doesn’t get burnt (about 10 min).
Add salt & pepper to taste.
Mix flour & baking powder.
Grate the Gruyère.
Mix the eggs & the oil w/ an electric handheld mixer until very well combined.
Add salt & pepper to taste.
Add the liquid mess to the flour & mix again.
Add the crème fraîche & mix again.
Fold in the onion-bacon mix as well as the Gruyère.
Pour the mess in the prepared loaf tin & let it bake for at least 45 min.
Make the famous test w/ the wooden pin... add another 5 min if necessary.
After removing from the oven let the loaf rest in the tin for about 10-15 min; afterwards lift the loaf out of the tin & let it rest again.
Remove the baking parchment carefully. The cake is rather soft when coming out of the oven.