Preheat your oven to 300 degrees. We are going to need a dutch oven or other heavy, oven proof pot with a tight fitting lid.
Let's make the garlic paste. You can see the different methods to make the paste in the blog post under Quick Kitchen Tips. Either way you choose to make it will result in a pungent paste that we are going to insert into the pork tenderloin. Split the paste so you have enough for both tenderloins.
We are going to season the pork tenderloins with the salt and pepper. Season both tenderloins well.
Cut a 1" slit down the wide side of both pork tenderloins. Smear the paste into the slit.
Heat a dutch oven over high heat. Add in the bacon fat. When the fat is shimmering, add in the tenderloins and allow to brown for 3-4 minutes without moving them. If you move them too much, the garlic paste will fall out. Using tongs, flip the tenderloins and cook for another 3-4 minutes. When they are browned, remove from the dutch oven and set aside.
Reduce the heat to medium-high. Add the olive oil and the onions, with a pinch of salt. Let the onions cook for 1-2 minutes, stirring well and scraping the browned bits off the bottom of the pot. Add in the carrots and celery. Allow to cook, stirring occasionally, for another 6-8 minutes.
Add in the dried herbs, mix well.
Add in the red wine. Turn the heat to high. Allow to almost completely cook off.
Add in the diced tomatoes. Stir well to combine and turn off the heat.
Add the browned pork tenderloins back into the pot, right on top of the veggies.
Cover with the lid and place in the oven for 2 hours.
When you remove from the oven, pull the tenderloins from the dutch oven to a cutting board. Slice against the grain into about ½" slices. Cover with foil and set aside.
Remove the veggies from the dutch oven and add to a serving dish. Layer the sliced pork over the veggies and serve hot. Enjoy!