For the marinade, whip together vinegar, mustard, garlic, black pepper, tarragon and salt in a bowl.
Slowly pour in LouAna Peanut Oil while whipping constantly until all of the oil is incorporated. Reserve a small amount of dressing for later use.
Coat hens with marinade, refrigerate and allow hens to marinate four hours up to overnight.
Fire up BBQ pit or gas grill and grill hens breast side down covered for 15 minutes being careful not to burn. Reserve marinade.
Flip hens, baste with marinade and cook for additional 20 minutes covered. Baste one more time, flip and cook for an additional 5 minutes.
Coat tomato slices and asparagus spears with remaining dressing and towards end of cooking process grill tomatoes until just heated. Allow asparagus to cook until slightly charred.
Place hens on large serving platter and garnish with grilled tomatoes and asparagus.
For a low fat entrée, serve Grilled Cornish Hens with a Spring Salad.