For the tuna: Remove the tuna from the refrigerator 20 minutes before grilling. Heat a charcoal or gas grill to high for direct grilling. Mix together the fennel, salt and pepper in a small bowl.
Brush the tuna with canola oil on both sides and sprinkle with the spice mixture. Grill until charred on both sides and cooked to medium doneness, about 5 minutes per side. Remove and let rest for 5 minutes. Cut into medium dice.
For the salad dressing: Whisk together the lemon juice, vinegar, mustard, rosemary, anchovies and garlic in a small bowl and season with salt and pepper. Slowly pour in the olive oil while whisking, until it all emulsifies. For a sweeter and thicker texture, whisk in a teaspoon of honey at a time, until desired taste and consistency is reached.
For the salad: Combine the beans, olives, fennel, onion and tuna in a large bowl. Add the dressing and gently toss to coat. Add the greens, basil and parsley , season with salt and pepper, and toss again.
For serving: Mound the salad on a platter and sprinkle the remaining lemon juice over the top.