At first, not knowing how it looks, I thought it is yellow poppy.
But then seeing pictures of it I now know that it is something else. But what?
I especially like the flame-formed orange to yellow color gradient on the petals.
Found in France on a meadow. It was quite wet during this spring and relatively warm as well.
It's the California poppy (Eschscholzia californica).
The main identifying characteristic is the single flower with four petals in yellow and orange. They come in various shades from a middle yellow to a deep orange, and can be single colored or have a gradation like in your photos.
The leaves are alternate on the stems, and are somewhat feathery with deeply divided leaflets.
It's native to the western US, but naturalizes easily in warm dry climates. It can be perennial if conditions suit it, and it reseeds itself well so even if it's in a climate where it grows as an annual, you can have a sustainable population.
