1Heat 1 tablespoon of the grapeseed oil in a medium frying pan over high heat. Add tomatoes and sear until the skins pucker and begin to color, about 2 minutes. (Be careful: When the tomatoes get hot, some might burst.) Add garlic and shallot and cook until slightly softened, about 1 minute more.
2Transfer to a blender, add vinegar, and blend on high until smooth. Slowly add remaining grapeseed oil and olive oil in a thin, steady stream, blending constantly until smooth. Season with salt and freshly ground black pepper and add herbs. Use immediately or cover and refrigerate for up to a week.