Start by combining your boneless top sirloin roast with all the seasoning ingredients in a large bowl. Cover and refrigerate for at least 4 hours or overnight.

In a heavy-bottomed pot, heat the vegetable oil over medium-high heat. Add the marinated roast and sear it on all sides for about 4-5 minutes until a golden-brown crust forms.

In the same pot, add chopped onion, minced garlic, carrots, and celery. Sauté for around 5 minutes until the vegetables soften.

Pour in 3 to 4 cups of beef broth, using a wooden spoon to scrape up any brown bits stuck to the bottom of the pot. Bring the broth to a gentle simmer.

Return the seared roast to the pot, adding the whole scotch bonnet pepper and fresh thyme. Cover the pot and reduce the heat to low. Simmer for 2.5 to 3 hours.

About 30 minutes before the roast is done, add the baby potatoes to the pot. Continue to simmer.

Once the meat is fork-tender and the potatoes are soft, remove the pot from heat. Let the roast rest for 10 minutes before slicing it against the grain.