For the caramelized onions:
Thinly slice onions and separate into rounds. Place in a large skillet over medium-high heat. Add the olive oil, a drizzle of local honey and sea salt. Then add the butter on top and let melt down into the onions. Continue to cook down until the onions are somewhat transparent, gooey and quite sticky with some of the ends crispy. Remove from heat and set aside.
For the horseradish cream sauce:
In a bowl, add all the ingredients and stir to mix well. Set aside.
For the dry rub:
In a small bowl, add all the ingredients and stir to combine well.
For the steak:
1. Coat the tri-tip with the dry rub, cover with plastic wrap and place in fridge for at least 3 hours (could be up to a day). Remove and let set at room temperature for 30 minutes before transferring to the grill.
2. Heat grill to 500°F.
3. Sear meat on both sides for approximately 5-6 minutes. Remove from direct heat and place on the indirect side of the grill or reduce heat to medium-high (approximately 350°F). Continue to cook until internal temperature reaches 130°F, approximately 20-25 minutes.
4. Place tri-tip on cutting board and let rest for 12-15 minutes before thinly slicing (across the grain). Then sprinkle with a little more kosher salt.
Drizzle the bottom of the New Orleans French bread, drizzle with the horseradish sauce and top with the meat, cheese, watercress and a final drizzle of the sauce.