Let your steak come to room temperature then pat it dry well with paper towel
Season both sides with salt and pepper
Heat a large skillet (cast iron preferred but not required)
Once hot add a drizzle of olive or avocado oil and add steak
Cook 3 minutes per side on medium high heat
Lower heat to medium, add butter, garlic & rosemary. Baste the steak with melted butter for an extra 2 minutes.
Remove steak and let rest on a cutting board for at least 5 minutes
Meanwhile slice baguette & add to frying pan with olive oil
Cook slices 2 minutes per side until they are golden
Slice steak against the grain
Place crostini on a serving platter & top with cheese
Layer on a piece of arugula and a piece of steak
Drizzle with balsamic glaze
Serve immediately