Heat a large skillet over medium-high, then add in oil and ground beef.
Cook, while stirring and breaking up the meat with a wooden spoon, until beef is nicely browned.
Drain excess grease.
Sprinkle meat with all the seasonings, and continue to cook stirring frequently for 2 minutes. Add in the tomato paste and water and bring everything to a low simmer, stirring all the brown bits from the bottom of the pan.
Simmer until the liquid is reduced, about 4-5 minutes.
While the beef is cooking, prepare your tomatoes.
Place each tomato stem side down on your cutting board. Using a sharp knife, carefully slice the tomatoes into 6 wedges, not going all the way through the stem, so the wedges hold together by the stem.
Gently pull tomatoes apart or open the wedges.
To assemble your taco tomatoes, fill each tomato as shown with a big spoonful (or two) of taco meat, followed by shredded lettuce, cheese and finish with a dollop of yogurt.
Serve immediately and enjoy.