Set an oven rack in the middle position and preheat the oven to 450°F

Season the beef all over with salt. In a large oven-proof skillet over medium-high, add a glug of oil and then the beef. Sear on all sides, about 10 minutes total

Transfer the skillet directly to the preheated oven and roast for about 15 minutes, until a thermometer inserted into the center of the meat registers 120°F

Transfer the meat to a cutting board and let it rest, covered loosely with aluminum foil, for 10 minutes

Meanwhile, in a medium saucepan over medium heat, melt the butter. Add ½ the pouch of Chimichurri, the wine, 2 cups of beef broth, and a pinch of salt. Bring to a simmer and cook for about 20 minutes, until the liquid is reduced by about half

In a small bowl, mix the remaining ½ cup of broth with the flour to make a slurry

Once the wine mixture is reduced, lower the heat to low and whisk in the slurry, until the sauce is thickened. Slice the tenderloin into slices and drizzle with the chimi-wine sauce