Ingredients:

• 2lb-2.5lb of beef sirloin steak
• 1 big bell pepper
• 2-3 roma tomatoes
• 1-2 onions
• Olive oil, about 3/4 of cup
• Salt to taste
• 
  Spices:
  4 tsp of ground oregano
• 2 tsp of ground black pepper
• 2 tsp of ground cumin
• 2 tsp ground marjoram
• 1 tsp of ground coriander seed
• 1 tsp of chili powder

How to prepare, step-by-step:

1. Prepare ingredients:

   

2. Clean beef, slice it in portion pieces, put into food container (I use one with plastic lid):

   

3. Peel onions, slice them in half circles, add to the container:

   

4. Clean bell pepper, slice it in stripes, add them to meat:

   

5. Blanch tomatoes, keep seeds in, slice:

   

6. Season with mix of spices and salt to taste, then mix:

   

7. Add olive oil:

   

8. Mix everything:

   

9. Cover food container with a lid of plastic wrap and put to fridge for couple of hours to marinate:

   

10. Sear portion of gyros meat with vegetables right before you are going to serve it (marinated left over meat can stay uncooked for couple of days in the fridge, just sear it portion by portion before you are planning to eat it). For that scoop meat along with vegetables and marinate to a hot heated frying pan; oil in the marinate should be enough for cooking:

    

11. Sear gyros until desired readiness, stir from time to time to ensure meat cooks evenly:

    

12. Serve with boiled rice or potatoes along with Tzatziki sauce: