In a large mixing bowl, whisk together apple cider vinegar, honey and mustard. Add olive oil while whisking. Add apples, spinach and cashews on top. (Wait to toss until just before serving.)
Heat a saute pan over medium-high heat. Add cooking oil and then bell peppers, asparagus and shallots to heated oil. Saute until vegetables are starting to turn tender, 3 to 4 minutes. Add Cajun seasoning and give the dish a good stir to combine.
Add butter to vegetables. When butter is melted add shrimp. Season shrimp with some salt and pepper as it cooks. Cook shrimp for 2 minutes and then add garlic. Continue cooking until shrimp is opaque / cooked through, ~2 minutes more.
Remove pan from heat and squeeze lemon juice over top. Season with some salt and black pepper.