Dry-off the roast with paper towels. Smear some peanut oil over all sides of the roast. Heat up a 10 inch aluminium skillet over a medium flame. Sear the roast on all sides in the hot pan. Season with salt and pepper. De-grease the pan. Find a meat rack to fit into the pan. Arrange the roast on the rack. Place the pan into the oven. Roast the pork, turning periodically, until the internal temperature reaches 150 degrees F, about 40 - 45 minutes. Remove the roast from the oven, re-plate it and allow the meat to rest for 10 minutes. The heat trapped in the tissues will continue to cook it until it becomes a perfect medium-well, juicy with a suggestion of pink.
De-grease the pan. Melt the butter in the pan over a medium flame. Whisk in the flour and continue whisking until the flour takes on a light brown color. Throw in the onions, reduce the flame, season them with salt and sweat the onions down. Toss in the garlic. Saute for about a minute. Add the tomatoes and warm them through. Pour in the wine and whisk to combine. Sprinkle in the cayenne pepper. Pour whatever juices have collected from underneath the plated roast into the pan. Reduce the sauce until it coats the back of a spoon. Season to taste with salt and pepper. Carve the roast into thick slices. Serve the roast and the sauce over bland rice, pasta or even smashed up, roasted potatoes.
For those who prefer a very rich sauce, pour in 2 oz of heavy cream and reduce after the adding the wine.