In a heavy bottomed saucepan
, over medium-high heat, add the grapeseed oil
. When the oil is hot add the onion
and saute until translucent, 3 to 4 minutes, stirring throughout. Deglaze
the pan with wine
. Once the pan has been deglazed add the stock, tomatoes, rosemary
, and parsley.
Reduce the sauce until it is reduced by 40 percent, about 15 to 20 minutes. Once the sauce has reduced, remove from heat and pour through a chinois
into a bowl. Return the sauce to the pan and stir in butter to finish the sauce. Sauce can be held warm until serving or stored in a covered container in the refrigerator.