Make cilantro lime dressing - Combine cilantro (if you don’t have an immersion blender, finely chop cilantro first), lime juice, vinegar, mustard, honey, salt, and olive oil. Blend with an immersion blender until nearly smooth. (Can be done up to 5 days ahead)
Make cilantro-lime butter - Heat butter in the microwave just until melted. Stir in cilantro lime dressing (portion for fish). Refrigerate until ready to use. (Can be done up to 5 days ahead)
Fish - Rinse fish and pat dry. Score the halibut with a knife by slicing through the skin a few times about 1/4" / .6 cm deep (this will help the fish to cook evenly). Season halibut with cumin, lime zest, and some salt.
Snap peas / Radishes / Lettuce - Prep as directed.
Heat a nonstick pan or skillet over medium-high heat. Add cooking oil and then halibut to heated oil. Sear fish on one side until golden brown, ~4 minutes. Flip and cook on the other side until the fish flakes easily, 2 to 4 minutes.
Toss together snap peas, radishes, avocados, and lettuce. Add cilantro-lime dressing (portion for salad) until dressed to your liking.
Spread cilantro-lime butter over warm fish. Serve fish with salad on the side. Enjoy!