How to make
Cut the onion into small pieces. Caramelize it in butter. Add the rum and once the alcohol evaporates, add the orange juice.
Add salt and rosemary. Wait for the water to boil slightly and turn off the stove.
Remove the rosemary and puree the sauce. Strain it.
Place the sauce back onto the hob.
Mix the starch / flour with enough water to dissolve it. Add it to meat sauce. Wait for it to thicken to the density you want.
The orange sauce is suitable for chicken and pork chops.