Slice the roast crosswise into 3 even steaks. Heat a cast-iron skillet over medium-high heat. Brush the steaks all over with 1 tablespoon olive oil, season with the chili powder and add salt to taste. Cook until a thermometer inserted into the side registers 125 degrees for medium-rare, 4 to 5 minutes per side. Let rest for 5 minutes.
Meanwhile, toss the tomatoes and hearts of palm in a bowl with the remaining 1 tablespoon olive oil, 1 tablespoon lime juice, and salt and pepper to taste.
Halve and pit the avocado; scoop the flesh into a blender or food processor. Add the cilantro, garlic, the remaining 1 tablespoon lime juice and 1/2 cup water; puree. Season with salt.
Thinly slice the steaks. Serve with the avocado sauce, tomato salad and tortillas for wrapping, if desired. Garnish with lime wedges.
Per serving: Calories 325; Fat 17 g (Sat. 3.3 g; Mono. 10.2 g; Poly. 1.8 g); Cholesterol 58 mg; Sodium 337 mg; Carbohydrate 9 g; Fiber 5 g; Protein 35 g