Place a rack in the top third of the oven and preheat to 400°F.
In a small bowl, stir together the mustard, honey, garlic, onion powder, paprika, and chili powder. Season with salt and pepper. Place the salmon on a baking sheet. Rub with the mustard mixture, then drizzle with the olive oil.
Bake until the salmon is warm in the center and turning opaque, 8 to 10 minutes, or longer to your liking. For the last 1 to 2 minutes, turn the oven to broil and broil until the salmon is browned on top.
Meanwhile, make the salad: In a medium bowl, combine the avocados, feta, cilantro, green onions, and serrano. Add the olive oil, lemon juice, and lime juice and toss gently to mix. Season with salt.
Make the honey mustard sauce: In a medium bowl, combine the grainy Dijon, mayo, honey, lemon juice, and vinegar. Season with salt and pepper and whisk to combine.
Divide the rice among bowls and add the salmon. Top with the avocado salad and spoon the honey mustard sauce on top.
