Place the avocado, tomatillos, and red onion into a bowl, and mix in juice of 2 lemons and olive oil. Set aside in refrigerator.
Preheat oven to 400 degrees F (200 degrees C).
Whisk peanut butter, red curry paste, and sesame seed oil together in a saucepan until smooth, and gradually whisk in the cream, a little at a time. Bring to a simmer over medium heat. Reduce heat, and simmer the cream mixture until reduced by half, about 15 minutes; whisk in the juice of 2 more lemons.
Bring a pot of water to a boil over medium heat, and simmer the yucca strips until they start to become tender, 8 to 9 minutes. Remove yucca pieces, and dry on paper towels. Heat 2 tablespoons vegetable oil in a skillet, and fry the yucca pieces until crisp and browned, 5 to 8 minutes. Drain yucca fries on paper towels.
Heat 1 more teaspoon of vegetable oil in an oven-safe skillet over medium-high heat until the oil shimmers with heat. Sear the grouper fillet until the outside is browned but the flesh is still translucent, about 1 minute per side. Sprinkle with salt and black pepper.
Place the skillet into the preheated oven, and cook the grouper until just opaque, about 10 minutes. Serve fillet with the yucca fries, topped with curry cream sauce and avocado-tomatillo salsa.