Preheat the oven to 200C, fan-forced. Line a large oven tray with baking paper. Peel the potatoes and cut into 3cm chunks. Put in a medium saucepan of cold salted water, bring to the boil and cook over medium heat for 10 mins or until almost tender. Drain. Put the potato on one half of the lined tray, drizzle with 1 tbs olive oil and season with salt and pepper. Roast for 10 mins.
Step 2 — Prep onions and stock
While the potato is boiling, cut the onions into thin wedges. Crumble the stock cubes into a heatproof jug, add 500ml (2 cups) boiling water and stir to dissolve. Put the onion in a roasting pan. Pour 180ml (¾ cup) of the stock into the pan.
Step 3 — Season and roast beef
Combine 3 tsp pepper and garlic seasoning (reduce the seasoning for a milder pepper kick) and 2 tsp olive oil in a large bowl and season with salt. Add the beef and turn to coat. Put the beef on the onion in the pan. Roast for 20 mins for medium-rare, or until cooked to your liking. Remove the beef from the pan and rest for 10 mins. Reserve the onion and pan juices.
Step 4 — Prep and roast vegetables
Meanwhile, quarter the carrot lengthwise. Peel the beetroot and cut into 1cm-thick wedges. Add to the tray with the potato, drizzle with 2 tsp olive oil and season with salt and pepper. Roast for 18 mins. Trim the baby broccoli, add to tray and drizzle with 2 tsp olive oil. Drizzle 2 tsp honey over the beetroot and carrot. Roast for a further 8 mins or until tender.
Step 5 — Start gravy
While the beef is resting, put the onion and pan juices in a medium frypan over medium-high heat. Cook, stirring, for 5 mins or until browned (this will give the gravy a good flavour and colour). Add 3 tsp flour and cook, stirring, for 2 mins or until browned.
Step 6 — Finish gravy and serve
Gradually add the remaining stock to the onion mixture, stirring constantly to prevent lumps forming. Bring to a simmer, reduce the heat to medium and cook, stirring, for 3 mins or until slightly thickened. Slice the beef. Divide the beef and roast vegetables among plates. Serve with the gravy.