1. Preheat oven to 425°.
2. Rub tenderloin with olive oil; season generously with salt and pepper. Tie "tail" under for uniform thickness and even cooking.
3. Roast in preheated oven or grill directly over high heat, lid down, 35-40 min. for rare (130° internal temperature) or 40-50 min. for medium (150° internal temperature). (If grilling, turn meat when grill marks form and meat releases easily from grates; grill until dark on all sides. Adjust heat down to medium-high if needed to prevent excess browning in last 20 min. or so.)
4. Remove from heat; tent loosely with foil and let rest for 10-15 min. before slicing.

DIJON AIOLI: In a small mixing bowl, combine ½ cup mayonnaise, ½ cup Dijon mustard and 1 tsp. garlic; season to taste with kosher salt and freshly ground Kowalski's Black Peppercorns. Refrigerate, covered, until ready to use. Makes 1 cup.