Cooking Tips
Garlic Butter Pork Tenderloin with Caramelized Onions
Juicy pork tenderloin in rich garlic butter sauce with golden caramelized onions, fresh thyme and a squeeze of lemon.
By Steak House Diaries Editorial Desk | Published | Updated | 2 min read
This is a dinner that tastes far fancier than the effort it takes: pork tenderloin seared until golden, finished in a garlic butter sauce sharpened with lemon and Dijon, and served over sweet, slow-cooked caramelized onions. The thyme ties the whole plate together. It is rich, savory and just a little zesty — the kind of meal that makes a weeknight feel like an occasion.
Ingredients
For the pork tenderloin: 700 g pork tenderloin; 2 tbsp olive oil; 2 tbsp unsalted butter; 4 garlic cloves, minced; 1 tsp paprika; 1 tsp garlic powder; ½ tsp onion powder; ½ tsp black pepper; 1 tsp salt, or to taste; 1 tsp dried thyme; 1 tbsp fresh lemon juice.
For the garlic butter sauce: 3 tbsp unsalted butter; 3 garlic cloves, minced; ½ cup chicken broth; 1 tbsp lemon juice; 1 tsp Dijon mustard; 1 tsp honey; ½ tsp black pepper; 1 tsp fresh thyme leaves.
For the caramelized onions: 2 large onions, thinly sliced; 2 tbsp butter; 1 tbsp olive oil; 1 tsp brown sugar (optional); ¼ tsp salt; ¼ tsp black pepper.
For garnishing: 2 tbsp fresh thyme leaves; 1 lemon, sliced; extra garlic butter sauce for drizzling.
Method
Start the onions first: melt the butter with the olive oil in a wide pan over medium-low heat, add the sliced onions and salt, and cook slowly for 25–30 minutes, stirring often, until deep golden and sweet. Stir in the brown sugar, if using, for the last 5 minutes. Set aside and keep warm.
Mix the paprika, garlic powder, onion powder, black pepper, salt and dried thyme. Pat the tenderloin dry and rub it all over with the spice mix.
Heat the olive oil in a large pan over medium-high heat. Sear the tenderloin for 3–4 minutes per side until deeply browned all over.
Lower the heat to medium, add the butter and garlic, and baste the pork with the foaming butter for 1–2 minutes. Splash in the lemon juice.
Cook until the thickest part of the pork reaches 145°F (63°C), then transfer to a board and rest for 5–10 minutes before slicing.
While the pork rests, make the sauce in the same pan: melt the butter, soften the garlic for 30 seconds, pour in the chicken broth and simmer for 2 minutes, scraping up the browned bits. Whisk in the lemon juice, Dijon mustard, honey, black pepper and thyme leaves.
Slice the pork, spoon over the garlic butter sauce, pile on the caramelized onions, and garnish with thyme leaves and lemon slices.
Cooking Tips
Caramelized onions cannot be rushed — low heat and patience are what turn them sweet instead of just soft.
Resting the pork is essential; slicing straight from the pan loses the juices that keep tenderloin tender.
Make the sauce in the same pan as the pork so it picks up all the browned, garlicky flavor.
Frequently asked questions
How do I know when pork tenderloin is done?
Use a thermometer: 145°F (63°C) at the thickest point, then rest for 5–10 minutes. The pork will be blush-pink inside, which is exactly right for tenderloin.
Can I make the caramelized onions ahead?
Yes — they keep well in the fridge for up to 4 days and reheat gently in a pan with a knob of butter.