Heat a large skillet over medium heat. Add the oil and heat until the oil is hot.
Add the onion to the oil and cook until translucent, 3-5 minutes.
Add the garlic to the onion, stir, and cook until fragrant, approximately 30 seconds.
Add the green beans, diced tomatoes, and stock to the skillet. Cover, reduce heat to low, and simmer until the green beans are cooked but still have a bite, approximately 15-20 minutes.
Remove the beans from the heat. Add the fresh basil and stir. Season to taste with salt, black pepper, and basil. If you want more sauce, add a little more stock. Serve immediately.
Notes
I love to keep my green beans whole, but you can also cut them into smaller pieces if desired.Frozen beans will also work! No need to defrost. They may cook more quickly.